From 5de65b5d6bf7d7293bf221f4fcdd6900e6146421 Mon Sep 17 00:00:00 2001
From: XhmikosR <xhmikosr@gmail.com>
Date: Sat, 4 Feb 2017 01:05:17 +0200
Subject: [PATCH 01/11] Viewer: fix "Export -> Save as..." in Firefox. (#1626)

For some weird reason, Firefox needs `document.body.appendChild(a)` too.
---
 lighthouse-viewer/app/src/lighthouse-report-viewer.js | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lighthouse-viewer/app/src/lighthouse-report-viewer.js b/lighthouse-viewer/app/src/lighthouse-report-viewer.js
index 05470ae1d6af..eb2f51f4a01d 100644
--- a/lighthouse-viewer/app/src/lighthouse-report-viewer.js
+++ b/lighthouse-viewer/app/src/lighthouse-report-viewer.js
@@ -361,9 +361,12 @@ class LighthouseViewerReport extends LighthouseReport {
     const a = document.createElement('a');
     a.download = `${filename}${ext}`;
     a.href = URL.createObjectURL(blob);
+    document.body.appendChild(a); // Firefox requires anchor to be in the DOM.
     a.click();
 
-    setTimeout(_ => URL.revokeObjectURL(a.href), 500); // cleanup.
+    // cleanup.
+    document.body.removeChild(a);
+    setTimeout(_ => URL.revokeObjectURL(a.href), 500);
   }
 
   /**

From 59f2f82018c8a4b3300b10593a24c35b32a957db Mon Sep 17 00:00:00 2001
From: Eric Bidelman <ebidel@gmail.com>
Date: Fri, 3 Feb 2017 17:00:15 -0800
Subject: [PATCH 02/11] CRX: make disabling extension during run optional
 (#1604)

---
 lighthouse-extension/app/popup.html           | 11 ++++-
 .../app/src/lighthouse-background.js          | 45 +++++++++++++------
 lighthouse-extension/app/src/popup.js         | 16 ++++---
 .../app/styles/lighthouse.css                 |  3 +-
 4 files changed, 53 insertions(+), 22 deletions(-)

diff --git a/lighthouse-extension/app/popup.html b/lighthouse-extension/app/popup.html
index d542293d044f..a12826d98abb 100644
--- a/lighthouse-extension/app/popup.html
+++ b/lighthouse-extension/app/popup.html
@@ -57,8 +57,17 @@ <h2 class="header-titles__url">...</h2>
   </aside>
 
   <aside class="options subpage">
-    <h2 class="options__title">Options</h2>
+    <h2 class="options__title">Settings</h2>
+    <div>
+      <label>
+        <input type="checkbox" class="setting-disable-extensions"
+               value="Disable other extensions while Lighthouse audits a page">Disable other extensions while Lighthouse audits a page.
+      </label>
+    </div>
+
+    <h2 class="options__title">Audit collections to include in report</h2>
     <ul class="options__list">
+      <!-- filled dynamically -->
     </ul>
 
     <button class="button button--ok" id="ok">OK</button>
diff --git a/lighthouse-extension/app/src/lighthouse-background.js b/lighthouse-extension/app/src/lighthouse-background.js
index 617e25d0098c..25b9dcbb36c1 100644
--- a/lighthouse-extension/app/src/lighthouse-background.js
+++ b/lighthouse-extension/app/src/lighthouse-background.js
@@ -26,8 +26,10 @@ const log = require('../../../lighthouse-core/lib/log');
 const ReportGenerator = require('../../../lighthouse-core/report/report-generator');
 
 const STORAGE_KEY = 'lighthouse_audits';
+const SETTINGS_KEY = 'lighthouse_settings';
 
 let installedExtensions = [];
+let disableExtensionsDuringRun = false;
 let lighthouseIsRunning = false;
 let latestStatusLog = [];
 
@@ -41,6 +43,10 @@ const _flatten = arr => [].concat(...arr);
  * @param {!Promise}
  */
 function enableOtherChromeExtensions(enable) {
+  if (!disableExtensionsDuringRun) {
+    return Promise.resolve();
+  }
+
   const str = enable ? 'enabling' : 'disabling';
   log.log('Chrome', `${str} ${installedExtensions.length} extensions.`);
 
@@ -251,27 +257,34 @@ window.getDefaultAggregations = function() {
 
 /**
  * Save currently selected set of aggregation categories to local storage.
- * @param {!Array<{name: string, audits: !Array<string>}>} selectedAggregations
+ * @param {{selectedAggregations: !Array<string>, disableExtensions: boolean}} settings
  */
-window.saveSelectedAggregations = function(selectedAggregations) {
+window.saveSettings = function(settings) {
   const storage = {
-    [STORAGE_KEY]: {}
+    [STORAGE_KEY]: {},
+    [SETTINGS_KEY]: {}
   };
 
+  // Stash selected aggregations.
   window.getDefaultAggregations().forEach(audit => {
-    storage[STORAGE_KEY][audit.name] = selectedAggregations.includes(audit.name);
+    storage[STORAGE_KEY][audit.name] = settings.selectedAggregations.includes(audit.name);
   });
 
+  // Stash disable extensionS setting.
+  disableExtensionsDuringRun = settings.disableExtensions;
+  storage[SETTINGS_KEY].disableExtensions = disableExtensionsDuringRun;
+
+  // Save object to chrome local storage.
   chrome.storage.local.set(storage);
 };
 
 /**
  * Load selected aggregation categories from local storage.
- * @return {!Promise<!Object<boolean>>}
+ * @return {!Promise<{selectedAggregations: !Object<boolean>, disableExtensions: boolean}>}
  */
-window.loadSelectedAggregations = function() {
+window.loadSettings = function() {
   return new Promise(resolve => {
-    chrome.storage.local.get(STORAGE_KEY, result => {
+    chrome.storage.local.get([STORAGE_KEY, SETTINGS_KEY], result => {
       // Start with list of all default aggregations set to true so list is
       // always up to date.
       const defaultAggregations = {};
@@ -279,13 +292,19 @@ window.loadSelectedAggregations = function() {
         defaultAggregations[aggregation.name] = true;
       });
 
-      // Load saved aggregation selections.
-      const savedSelections = result[STORAGE_KEY];
+      // Load saved aggregations and settings, overwriting defaults with any
+      // saved selections.
+      const savedAggregations = Object.assign(defaultAggregations, result[STORAGE_KEY]);
 
-      // Overwrite defaults with any saved aggregation selections.
-      resolve(
-        Object.assign(defaultAggregations, savedSelections)
-      );
+      const defaultSettings = {
+        disableExtensions: disableExtensionsDuringRun
+      };
+      const savedSettings = Object.assign(defaultSettings, result[SETTINGS_KEY]);
+
+      resolve({
+        selectedAggregations: savedAggregations,
+        disableExtensions: savedSettings.disableExtensions
+      });
     });
   });
 };
diff --git a/lighthouse-extension/app/src/popup.js b/lighthouse-extension/app/src/popup.js
index 8c2b7ae10405..b0176a4bd923 100644
--- a/lighthouse-extension/app/src/popup.js
+++ b/lighthouse-extension/app/src/popup.js
@@ -189,12 +189,14 @@ function initPopup() {
 
     background.listenForStatus(logStatus);
 
-    background.loadSelectedAggregations().then(selectedAggregations => {
-      generateOptionsList(background, selectedAggregations);
+    background.loadSettings().then(settings => {
+      generateOptionsList(background, settings.selectedAggregations);
+
+      document.querySelector('.setting-disable-extensions').checked = settings.disableExtensions;
 
       const generateReportButton = document.getElementById('generate-report');
       generateReportButton.addEventListener('click', () => {
-        onGenerateReportButtonClick(background, selectedAggregations);
+        onGenerateReportButtonClick(background, settings.selectedAggregations);
       });
     });
 
@@ -206,10 +208,12 @@ function initPopup() {
 
     const okButton = document.getElementById('ok');
     okButton.addEventListener('click', () => {
-      // Save selected aggregation categories on options page close.
-      const checkedAggregations = Array.from(optionsEl.querySelectorAll(':checked'))
+      // Save settings when options page is closed.
+      const selectedAggregations = Array.from(optionsEl.querySelectorAll(':checked'))
           .map(input => input.value);
-      background.saveSelectedAggregations(checkedAggregations);
+      const disableExtensions = document.querySelector('.setting-disable-extensions').checked;
+
+      background.saveSettings({selectedAggregations, disableExtensions});
 
       optionsEl.classList.remove(subpageVisibleClass);
     });
diff --git a/lighthouse-extension/app/styles/lighthouse.css b/lighthouse-extension/app/styles/lighthouse.css
index 4a814a699ab3..81dec59d47c5 100644
--- a/lighthouse-extension/app/styles/lighthouse.css
+++ b/lighthouse-extension/app/styles/lighthouse.css
@@ -216,15 +216,14 @@ html, body {
 .options {
   overflow: auto; /* [1] */
   display: block;
+  text-align: left;
 }
 
 .options__title {
-  margin: 0 auto;
   font-weight: 300;
 }
 
 .options__list {
   padding: 0;
   list-style: none;
-  text-align: left;
 }

From ef8343dac7d5d89e0100a71952c263ce4b402a3a Mon Sep 17 00:00:00 2001
From: Paul Irish <paul.irish@gmail.com>
Date: Fri, 3 Feb 2017 17:37:42 -0800
Subject: [PATCH 03/11] fMP: Use last fMPCandidate if no FMP is marked. (#1632)

---
 .../audits/first-meaningful-paint.js          |  3 +-
 .../gather/computed/trace-of-tab.js           | 20 ++++-
 lighthouse-core/gather/driver.js              |  1 +
 .../lib/traces/pwmetrics-events.js            | 12 +--
 .../audits/first-meaningful-paint-test.js     | 18 +++-
 .../test/fixtures/traces/no_fmp_event.json    | 89 +++++++++++++++++++
 .../test/gather/computed/trace-of-tab-test.js |  9 ++
 7 files changed, 138 insertions(+), 14 deletions(-)
 create mode 100644 lighthouse-core/test/fixtures/traces/no_fmp_event.json

diff --git a/lighthouse-core/audits/first-meaningful-paint.js b/lighthouse-core/audits/first-meaningful-paint.js
index ca97a837d9d6..d1b82c3e75c8 100644
--- a/lighthouse-core/audits/first-meaningful-paint.js
+++ b/lighthouse-core/audits/first-meaningful-paint.js
@@ -53,9 +53,8 @@ class FirstMeaningfulPaint extends Audit {
   static audit(artifacts) {
     const trace = artifacts.traces[this.DEFAULT_PASS];
     return artifacts.requestTraceOfTab(trace).then(tabTrace => {
-      // Sometimes fMP is triggered before fCP
       if (!tabTrace.firstMeaningfulPaintEvt) {
-        throw new Error('No usable `firstMeaningfulPaint` event found in trace');
+        throw new Error('No usable `firstMeaningfulPaint(Candidate)` events found in trace');
       }
 
       // navigationStart is currently essential to FMP calculation.
diff --git a/lighthouse-core/gather/computed/trace-of-tab.js b/lighthouse-core/gather/computed/trace-of-tab.js
index afcaff09ae0f..56fea223b8ce 100644
--- a/lighthouse-core/gather/computed/trace-of-tab.js
+++ b/lighthouse-core/gather/computed/trace-of-tab.js
@@ -29,6 +29,7 @@
  */
 
 const ComputedArtifact = require('./computed-artifact');
+const log = require('../../lib/log');
 
 class TraceOfTab extends ComputedArtifact {
 
@@ -51,7 +52,8 @@ class TraceOfTab extends ComputedArtifact {
   compute_(trace) {
     // Parse the trace for our key events and sort them by timestamp.
     const keyEvents = trace.traceEvents.filter(e => {
-      return e.cat.includes('blink.user_timing') || e.name === 'TracingStartedInPage';
+      return e.cat.includes('blink.user_timing') || e.cat.includes('loading') ||
+          e.name === 'TracingStartedInPage';
     }).sort((event0, event1) => event0.ts - event1.ts);
 
     // The first TracingStartedInPage in the trace is definitely our renderer thread of interest
@@ -67,9 +69,23 @@ class TraceOfTab extends ComputedArtifact {
         e.name === 'navigationStart' && e.ts < firstFCP.ts).pop();
 
     // fMP will follow at/after the FCP, though we allow some timestamp tolerance
-    const firstMeaningfulPaint = frameEvents.find(e =>
+    let firstMeaningfulPaint = frameEvents.find(e =>
         e.name === 'firstMeaningfulPaint' && e.ts >= (firstFCP.ts - TraceOfTab.fmpToleranceMs));
 
+    // If there was no firstMeaningfulPaint event found in the trace, the network idle detection
+    // may have not been triggered before Lighthouse finished tracing.
+    // In this case, we'll use the last firstMeaningfulPaintCandidate we can find.
+    // However, if no candidates were found (a bogus trace, likely), we fail.
+    if (!firstMeaningfulPaint) {
+      const fmpCand = 'firstMeaningfulPaintCandidate';
+      log.verbose('trace-of-tab', `No firstMeaningfulPaint found, falling back to last ${fmpCand}`);
+      const lastCandidate = frameEvents.filter(e => e.name === fmpCand).pop();
+      if (!lastCandidate) {
+        log.verbose('trace-of-tab', 'No `firstMeaningfulPaintCandidate` events found in trace');
+      }
+      firstMeaningfulPaint = lastCandidate;
+    }
+
     // subset all trace events to just our tab's process (incl threads other than main)
     const processEvents = trace.traceEvents.filter(e => {
       return e.pid === startedInPageEvt.pid;
diff --git a/lighthouse-core/gather/driver.js b/lighthouse-core/gather/driver.js
index 639ee8eb1c79..8c30eb860ff6 100644
--- a/lighthouse-core/gather/driver.js
+++ b/lighthouse-core/gather/driver.js
@@ -49,6 +49,7 @@ class Driver {
       'blink.console',
       'blink.user_timing',
       'benchmark',
+      'loading',
       'latencyInfo',
       'devtools.timeline',
       'disabled-by-default-devtools.timeline',
diff --git a/lighthouse-core/lib/traces/pwmetrics-events.js b/lighthouse-core/lib/traces/pwmetrics-events.js
index 1df54eb41888..13122e3c6c98 100644
--- a/lighthouse-core/lib/traces/pwmetrics-events.js
+++ b/lighthouse-core/lib/traces/pwmetrics-events.js
@@ -145,10 +145,10 @@ class Metrics {
    *     { "pid": 89922,"tid":1295,"ts":77176783452,"ph":"b","cat":"blink.user_timing","name":"innermeasure","args":{},"tts":1257886,"id":"0xe66c67"}
    *     { "pid": 89922,"tid":1295,"ts":77176882592,"ph":"e","cat":"blink.user_timing","name":"innermeasure","args":{},"tts":1257898,"id":"0xe66c67"}
    * @param {{ts: number, id: string, name: string}} metric
-   * @param {number} navStartTs
+   * @param {{ts: number, id: string, name: string}} navStart
    * @return {!Array} Pair of trace events (start/end)
    */
-  synthesizeEventPair(metric, navStartTs) {
+  synthesizeEventPair(metric, navStart) {
     // We'll masquerade our fake events to look mostly like navigationStart
     const eventBase = {
       pid: this.getNavigationStartEvt().pid,
@@ -160,7 +160,7 @@ class Metrics {
       id: `0x${((Math.random() * 1000000) | 0).toString(16)}`
     };
     const fakeMeasureStartEvent = Object.assign({}, eventBase, {
-      ts: navStartTs,
+      ts: navStart.ts,
       ph: 'b'
     });
     const fakeMeasureEndEvent = Object.assign({}, eventBase, {
@@ -182,8 +182,8 @@ class Metrics {
     }
 
     // confirm our navStart's correctly match
-    const navStartTs = metrics.find(e => e.id === 'navstart').ts;
-    if (this.getNavigationStartEvt().ts !== navStartTs) {
+    const navStartEvt = metrics.find(e => e.id === 'navstart');
+    if (!navStartEvt || this.getNavigationStartEvt().ts !== navStartEvt.ts) {
       log.error('pwmetrics-events', 'Reference navigationStart doesn\'t match fMP\'s navStart');
       return [];
     }
@@ -197,7 +197,7 @@ class Metrics {
         return;
       }
       log.verbose('pwmetrics-events', `Sythesizing trace events for ${metric.name}`);
-      fakeEvents.push(...this.synthesizeEventPair(metric, navStartTs));
+      fakeEvents.push(...this.synthesizeEventPair(metric, navStartEvt));
     });
     return fakeEvents;
   }
diff --git a/lighthouse-core/test/audits/first-meaningful-paint-test.js b/lighthouse-core/test/audits/first-meaningful-paint-test.js
index 310c1e03f995..901739e1aabc 100644
--- a/lighthouse-core/test/audits/first-meaningful-paint-test.js
+++ b/lighthouse-core/test/audits/first-meaningful-paint-test.js
@@ -22,6 +22,7 @@ const traceEvents = require('../fixtures/traces/progressive-app.json');
 const badNavStartTrace = require('../fixtures/traces/bad-nav-start-ts.json');
 const lateTracingStartedTrace = require('../fixtures/traces/tracingstarted-after-navstart.json');
 const preactTrace = require('../fixtures/traces/preactjs.com_ts_of_undefined.json');
+const noFMPtrace = require('../fixtures/traces/no_fmp_event.json');
 
 const GatherRunner = require('../../gather/gather-runner.js');
 const computedArtifacts = GatherRunner.instantiateComputedArtifacts();
@@ -69,8 +70,8 @@ describe('Performance: first-meaningful-paint audit', () => {
     });
   });
 
-  describe('finds correct FMP in various traces', () => {
-    it('finds the fMP if there was a tracingStartedInPage after the frame\'s navStart', () => {
+  describe('finds correct FMP', () => {
+    it('if there was a tracingStartedInPage after the frame\'s navStart', () => {
       return FMPAudit.audit(generateArtifactsWithTrace(lateTracingStartedTrace)).then(result => {
         assert.equal(result.displayValue, '529.9ms');
         assert.equal(result.rawValue, 529.9);
@@ -80,7 +81,7 @@ describe('Performance: first-meaningful-paint audit', () => {
       });
     });
 
-    it('finds the fMP if there was a tracingStartedInPage after the frame\'s navStart #2', () => {
+    it('if there was a tracingStartedInPage after the frame\'s navStart #2', () => {
       return FMPAudit.audit(generateArtifactsWithTrace(badNavStartTrace)).then(result => {
         assert.equal(result.displayValue, '632.4ms');
         assert.equal(result.rawValue, 632.4);
@@ -90,7 +91,7 @@ describe('Performance: first-meaningful-paint audit', () => {
       });
     });
 
-    it('finds the fMP if it appears slightly before the fCP', () => {
+    it('if it appears slightly before the fCP', () => {
       return FMPAudit.audit(generateArtifactsWithTrace(preactTrace)).then(result => {
         assert.equal(result.displayValue, '878.4ms');
         assert.equal(result.rawValue, 878.4);
@@ -99,5 +100,14 @@ describe('Performance: first-meaningful-paint audit', () => {
         assert.ok(!result.debugString);
       });
     });
+
+    it('from candidates if no defined FMP exists', () => {
+      return FMPAudit.audit(generateArtifactsWithTrace(noFMPtrace)).then(result => {
+        assert.equal(result.displayValue, '4460.9ms');
+        assert.equal(result.rawValue, 4460.9);
+        assert.equal(result.extendedInfo.value.timings.fCP, 1494.73);
+        assert.ok(!result.debugString);
+      });
+    });
   });
 });
diff --git a/lighthouse-core/test/fixtures/traces/no_fmp_event.json b/lighthouse-core/test/fixtures/traces/no_fmp_event.json
new file mode 100644
index 000000000000..d84112d946da
--- /dev/null
+++ b/lighthouse-core/test/fixtures/traces/no_fmp_event.json
@@ -0,0 +1,89 @@
+{
+  "traceEvents": [
+    {
+      "pid": 77472,
+      "tid": 775,
+      "ts": 2146735802456,
+      "ph": "I",
+      "cat": "disabled-by-default-devtools.timeline",
+      "name": "TracingStartedInPage",
+      "args": {
+        "data": {
+          "frames": [
+            {
+              "frame": "0x150343381dd0",
+              "name": "",
+              "url": "about:blank"
+            }
+          ],
+          "page": "0x150343381dd0",
+          "sessionId": "77472.1"
+        }
+      },
+      "tts": 341067,
+      "s": "t"
+    },
+    {
+      "pid": 77472,
+      "tid": 775,
+      "ts": 2146735807738,
+      "ph": "R",
+      "cat": "blink.user_timing",
+      "name": "navigationStart",
+      "args": {
+        "frame": "0x150343381dd0"
+      },
+      "tts": 341944
+    },
+    {
+      "pid": 77472,
+      "tid": 775,
+      "ts": 2146737301957,
+      "ph": "I",
+      "cat": "blink.user_timing,rail",
+      "name": "firstPaint",
+      "args": {
+        "frame": "0x150343381dd0"
+      },
+      "tts": 549087,
+      "s": "p"
+    },
+    {
+      "pid": 77472,
+      "tid": 775,
+      "ts": 2146737302468,
+      "ph": "R",
+      "cat": "blink.user_timing,rail",
+      "name": "firstImagePaint",
+      "args": {
+        "frame": "0x150343381dd0"
+      },
+      "tts": 549603
+    },
+    {
+      "pid": 77472,
+      "tid": 775,
+      "ts": 2146737302468,
+      "ph": "I",
+      "cat": "blink.user_timing,rail",
+      "name": "firstContentfulPaint",
+      "args": {
+        "frame": "0x150343381dd0"
+      },
+      "tts": 549599,
+      "s": "p"
+    },
+    {
+      "pid": 77472,
+      "tid": 775,
+      "ts": 2146740268666,
+      "ph": "R",
+      "cat": "loading",
+      "name": "firstMeaningfulPaintCandidate",
+      "args": {
+        "frame": "0x150343381dd0"
+      },
+      "tts": 1009771
+    }
+  ]
+}
\ No newline at end of file
diff --git a/lighthouse-core/test/gather/computed/trace-of-tab-test.js b/lighthouse-core/test/gather/computed/trace-of-tab-test.js
index 43919be8f9de..7a5c823d2f56 100644
--- a/lighthouse-core/test/gather/computed/trace-of-tab-test.js
+++ b/lighthouse-core/test/gather/computed/trace-of-tab-test.js
@@ -22,6 +22,7 @@ const assert = require('assert');
 const badNavStartTrace = require('../../fixtures/traces/bad-nav-start-ts.json');
 const lateTracingStartedTrace = require('../../fixtures/traces/tracingstarted-after-navstart.json');
 const preactTrace = require('../../fixtures/traces/preactjs.com_ts_of_undefined.json');
+const noFMPtrace = require('../../fixtures/traces/no_fmp_event.json');
 
 /* eslint-env mocha */
 describe('Trace of Tab computed artifact:', () => {
@@ -63,5 +64,13 @@ describe('Trace of Tab computed artifact:', () => {
       assert.equal(trace.firstContentfulPaintEvt.ts, 1805797263653);
       assert.equal(trace.firstMeaningfulPaintEvt.ts, 1805797262960);
     });
+
+    it('from candidates if no defined FMP exists', () => {
+      const trace = traceOfTab.compute_(noFMPtrace);
+      assert.equal(trace.startedInPageEvt.ts, 2146735802456);
+      assert.equal(trace.navigationStartEvt.ts, 2146735807738);
+      assert.equal(trace.firstContentfulPaintEvt.ts, 2146737302468);
+      assert.equal(trace.firstMeaningfulPaintEvt.ts, 2146740268666);
+    });
   });
 });

From 049b85ce0b4f7ad51d6246937b965a73d15603b4 Mon Sep 17 00:00:00 2001
From: Brendan Kenny <bckenny@google.com>
Date: Mon, 30 Jan 2017 18:25:55 -0800
Subject: [PATCH 04/11] update ServiceWorker gatherer to use Errors for errors

---
 lighthouse-core/audits/service-worker.js            |  8 --------
 lighthouse-core/gather/gatherers/service-worker.js  |  5 -----
 lighthouse-core/test/audits/service-worker-test.js  | 13 -------------
 .../test/gather/gatherers/service-worker-test.js    | 13 -------------
 4 files changed, 39 deletions(-)

diff --git a/lighthouse-core/audits/service-worker.js b/lighthouse-core/audits/service-worker.js
index ef5dbe33c54e..aa404908cfc9 100644
--- a/lighthouse-core/audits/service-worker.js
+++ b/lighthouse-core/audits/service-worker.js
@@ -51,14 +51,6 @@ class ServiceWorker extends Audit {
    * @return {!AuditResult}
    */
   static audit(artifacts) {
-    if (!artifacts.ServiceWorker.versions) {
-      // Error in ServiceWorker gatherer.
-      return ServiceWorker.generateAuditResult({
-        rawValue: false,
-        debugString: artifacts.ServiceWorker.debugString
-      });
-    }
-
     // Find active service worker for this URL. Match against
     // artifacts.URL.finalUrl so audit accounts for any redirects.
     const version = getActivatedServiceWorker(
diff --git a/lighthouse-core/gather/gatherers/service-worker.js b/lighthouse-core/gather/gatherers/service-worker.js
index 49953f0aeb35..36d673090a7f 100644
--- a/lighthouse-core/gather/gatherers/service-worker.js
+++ b/lighthouse-core/gather/gatherers/service-worker.js
@@ -27,11 +27,6 @@ class ServiceWorker extends Gatherer {
         return {
           versions: data.versions
         };
-      })
-      .catch(err => {
-        return {
-          debugString: `Error in querying Service Worker status: ${err.message}`
-        };
       });
   }
 }
diff --git a/lighthouse-core/test/audits/service-worker-test.js b/lighthouse-core/test/audits/service-worker-test.js
index ce6ce85f65b8..2c6680763476 100644
--- a/lighthouse-core/test/audits/service-worker-test.js
+++ b/lighthouse-core/test/audits/service-worker-test.js
@@ -21,19 +21,6 @@ const assert = require('assert');
 /* eslint-env mocha */
 
 describe('Offline: Service Worker audit', () => {
-  it('reports driver error when given no Service Worker versions', () => {
-    const debugString = 'Error string';
-    const output = Audit.audit({
-      ServiceWorker: {
-        debugString
-      }
-    });
-
-    assert.equal(output.score, false);
-    assert.equal(output.rawValue, false);
-    assert.equal(output.debugString, debugString);
-  });
-
   it('passes when given a matching Service Worker version', () => {
     const output = Audit.audit({
       ServiceWorker: {
diff --git a/lighthouse-core/test/gather/gatherers/service-worker-test.js b/lighthouse-core/test/gather/gatherers/service-worker-test.js
index 179fe5bb67ab..abd112179b07 100644
--- a/lighthouse-core/test/gather/gatherers/service-worker-test.js
+++ b/lighthouse-core/test/gather/gatherers/service-worker-test.js
@@ -45,17 +45,4 @@ describe('Service Worker gatherer', () => {
       assert.deepEqual(artifact.versions, versions);
     });
   });
-
-  it('handles driver failure', () => {
-    return serviceWorkerGatherer.beforePass({
-      driver: {
-        getServiceWorkerVersions() {
-          return Promise.reject('fail');
-        }
-      }
-    }).then(artifact => {
-      assert.ok(!artifact.versions);
-      assert.ok(artifact.debugString);
-    });
-  });
 });

From b8c42f007e80e3f36dbfaf2612d689a69324c583 Mon Sep 17 00:00:00 2001
From: Brendan Kenny <bckenny@google.com>
Date: Thu, 2 Feb 2017 12:32:37 -0800
Subject: [PATCH 05/11] update ContentWidth gatherer to use Errors for errors

---
 lighthouse-core/audits/content-width.js              |  2 +-
 lighthouse-core/gather/gatherers/content-width.js    | 10 ++++------
 lighthouse-core/test/audits/content-width-test.js    | 11 -----------
 .../test/gather/gatherers/content-width-test.js      | 12 ------------
 4 files changed, 5 insertions(+), 30 deletions(-)

diff --git a/lighthouse-core/audits/content-width.js b/lighthouse-core/audits/content-width.js
index a697065184ae..5a460d11cf64 100644
--- a/lighthouse-core/audits/content-width.js
+++ b/lighthouse-core/audits/content-width.js
@@ -42,7 +42,7 @@ class ContentWidth extends Audit {
   static audit(artifacts) {
     const scrollWidth = artifacts.ContentWidth.scrollWidth;
     const viewportWidth = artifacts.ContentWidth.viewportWidth;
-    const widthsMatch = scrollWidth === viewportWidth && scrollWidth !== -1;
+    const widthsMatch = scrollWidth === viewportWidth;
 
     return ContentWidth.generateAuditResult({
       rawValue: widthsMatch,
diff --git a/lighthouse-core/gather/gatherers/content-width.js b/lighthouse-core/gather/gatherers/content-width.js
index f2d388dcad2c..2e1686a5feb1 100644
--- a/lighthouse-core/gather/gatherers/content-width.js
+++ b/lighthouse-core/gather/gatherers/content-width.js
@@ -34,6 +34,10 @@ function getContentWidth() {
 
 class ContentWidth extends Gatherer {
 
+  /**
+   * @param {!Object} options
+   * @return {!Promise<{scrollWidth: number, viewportWidth: number, devicePixelRatio: number}>}
+   */
   afterPass(options) {
     const driver = options.driver;
 
@@ -47,12 +51,6 @@ class ContentWidth extends Gatherer {
       }
 
       return returnedValue;
-    }, _ => {
-      return {
-        scrollWidth: -1,
-        viewportWidth: -1,
-        devicePixelRatio: -1,
-      };
     });
   }
 }
diff --git a/lighthouse-core/test/audits/content-width-test.js b/lighthouse-core/test/audits/content-width-test.js
index 5481771e0127..7298d5cdcf9b 100644
--- a/lighthouse-core/test/audits/content-width-test.js
+++ b/lighthouse-core/test/audits/content-width-test.js
@@ -33,17 +33,6 @@ describe('Mobile-friendly: content-width audit', () => {
     assert.ok(result.debugString);
   });
 
-  it('fails when gatherer failed', () => {
-    const result = Audit.audit({
-      ContentWidth: {
-        scrollWidth: -1,
-        viewportWidth: -1
-      }
-    });
-    assert.equal(result.rawValue, false);
-    assert.ok(result.debugString);
-  });
-
   it('passes when widths match', () => {
     return assert.equal(Audit.audit({
       ContentWidth: {
diff --git a/lighthouse-core/test/gather/gatherers/content-width-test.js b/lighthouse-core/test/gather/gatherers/content-width-test.js
index 3f38c33e27fe..2d7de7479993 100644
--- a/lighthouse-core/test/gather/gatherers/content-width-test.js
+++ b/lighthouse-core/test/gather/gatherers/content-width-test.js
@@ -43,16 +43,4 @@ describe('Content Width gatherer', () => {
       assert.ok(artifact.viewportWidth === 400);
     });
   });
-
-  it('handles driver failure', () => {
-    return contentWidthGatherer.afterPass({
-      driver: {
-        evaluateAsync() {
-          return Promise.reject('such a fail');
-        }
-      }
-    }).then(artifact => {
-      assert.equal(artifact.scrollWidth, -1);
-    });
-  });
 });

From fea5f7420dee396046d3dc9777e7037c777c9960 Mon Sep 17 00:00:00 2001
From: Brendan Kenny <bckenny@google.com>
Date: Thu, 2 Feb 2017 12:38:22 -0800
Subject: [PATCH 06/11] update HTTPS gatherer to use Errors for errors

---
 lighthouse-core/gather/gatherers/https.js      | 13 ++++---------
 .../test/gather/gatherers/https-test.js        | 18 ++++++++----------
 2 files changed, 12 insertions(+), 19 deletions(-)

diff --git a/lighthouse-core/gather/gatherers/https.js b/lighthouse-core/gather/gatherers/https.js
index e667ef61c910..da27925e28de 100644
--- a/lighthouse-core/gather/gatherers/https.js
+++ b/lighthouse-core/gather/gatherers/https.js
@@ -39,11 +39,6 @@ class HTTPS extends Gatherer {
         return {
           value: state.schemeIsCryptographic
         };
-      }, _ => {
-        return {
-          value: false,
-          debugString: 'Error requesting page security state.'
-        };
       });
 
     let noSecurityChangesTimeout;
@@ -51,10 +46,7 @@ class HTTPS extends Gatherer {
       // Set up a timeout for ten seconds in case we don't get any
       // security events at all. If that happens, bail.
       noSecurityChangesTimeout = setTimeout(_ => {
-        resolve({
-          value: false,
-          debugString: 'Timed out waiting for page security state.'
-        });
+        reject(new Error('Timed out waiting for page security state.'));
       }, timeout);
     });
 
@@ -65,6 +57,9 @@ class HTTPS extends Gatherer {
       // Clear timeout. No effect if it won, no need to wait if it lost.
       clearTimeout(noSecurityChangesTimeout);
       return result;
+    }).catch(err => {
+      clearTimeout(noSecurityChangesTimeout);
+      throw err;
     });
   }
 }
diff --git a/lighthouse-core/test/gather/gatherers/https-test.js b/lighthouse-core/test/gather/gatherers/https-test.js
index ae15aba41941..ede395b0c4cc 100644
--- a/lighthouse-core/test/gather/gatherers/https-test.js
+++ b/lighthouse-core/test/gather/gatherers/https-test.js
@@ -41,20 +41,19 @@ describe('HTTPS gatherer', () => {
     });
   });
 
-  it('handles driver failure', () => {
+  it('throws an error on driver failure', () => {
     return httpsGather.afterPass({
       driver: {
         getSecurityState() {
           return Promise.reject('such a fail');
         }
       }
-    }).then(artifact => {
-      assert.equal(artifact.value, false);
-      assert.ok(artifact.debugString);
-    });
+    }).then(
+      _ => assert.ok(false),
+      _ => assert.ok(true));
   });
 
-  it('handles driver timeout', () => {
+  it('throws an error on driver timeout', () => {
     const fastTimeout = 50;
     const slowResolve = 200;
 
@@ -72,9 +71,8 @@ describe('HTTPS gatherer', () => {
       },
 
       _testTimeout: fastTimeout
-    }).then(artifact => {
-      assert.equal(artifact.value, false);
-      assert.ok(artifact.debugString);
-    });
+    }).then(
+      _ => assert.ok(false),
+      _ => assert.ok(true));
   });
 });

From 1f40ea2b60813bba494705087235fb39349bfdd9 Mon Sep 17 00:00:00 2001
From: Brendan Kenny <bckenny@google.com>
Date: Thu, 2 Feb 2017 12:52:40 -0800
Subject: [PATCH 07/11] update HTTPRedirect gatherer to use Errors for errors

---
 .../gather/gatherers/http-redirect.js            | 13 ++++---------
 .../test/audits/redirects-http-test.js           |  2 +-
 .../test/gather/gatherers/http-redirect-test.js  | 16 +++++++---------
 3 files changed, 12 insertions(+), 19 deletions(-)

diff --git a/lighthouse-core/gather/gatherers/http-redirect.js b/lighthouse-core/gather/gatherers/http-redirect.js
index b9632c5c4cdd..0770d0c23645 100644
--- a/lighthouse-core/gather/gatherers/http-redirect.js
+++ b/lighthouse-core/gather/gatherers/http-redirect.js
@@ -47,11 +47,6 @@ class HTTPRedirect extends Gatherer {
         return {
           value: state.schemeIsCryptographic
         };
-      }, _ => {
-        return {
-          value: false,
-          debugString: 'Error requesting security state'
-        };
       });
 
     let noSecurityChangesTimeout;
@@ -59,10 +54,7 @@ class HTTPRedirect extends Gatherer {
       // Set up a timeout for ten seconds in case we don't get any
       // security events at all. If that happens, bail.
       noSecurityChangesTimeout = setTimeout(_ => {
-        resolve({
-          value: false,
-          debugString: 'Timed out waiting for HTTP redirection.'
-        });
+        reject(new Error('Timed out waiting for HTTP redirection.'));
       }, timeout);
     });
 
@@ -73,6 +65,9 @@ class HTTPRedirect extends Gatherer {
       // Clear timeout. No effect if it won, no need to wait if it lost.
       clearTimeout(noSecurityChangesTimeout);
       return result;
+    }).catch(err => {
+      clearTimeout(noSecurityChangesTimeout);
+      throw err;
     });
   }
 }
diff --git a/lighthouse-core/test/audits/redirects-http-test.js b/lighthouse-core/test/audits/redirects-http-test.js
index 1f10dc2deef7..4a537795ce5c 100644
--- a/lighthouse-core/test/audits/redirects-http-test.js
+++ b/lighthouse-core/test/audits/redirects-http-test.js
@@ -18,7 +18,7 @@
 const Audit = require('../../audits/redirects-http.js');
 const assert = require('assert');
 
-/* global describe, it*/
+/* eslint-env mocha */
 
 describe('Security: HTTP->HTTPS audit', () => {
   it('fails when no redirect detected', () => {
diff --git a/lighthouse-core/test/gather/gatherers/http-redirect-test.js b/lighthouse-core/test/gather/gatherers/http-redirect-test.js
index 144daf3c83ad..81406226e831 100644
--- a/lighthouse-core/test/gather/gatherers/http-redirect-test.js
+++ b/lighthouse-core/test/gather/gatherers/http-redirect-test.js
@@ -69,17 +69,16 @@ describe('HTTP Redirect gatherer', () => {
     });
   });
 
-  it('handles driver failure', () => {
+  it('throws an error on driver failure', () => {
     return httpRedirectGather.afterPass({
       driver: {
         getSecurityState() {
           return Promise.reject('such a fail');
         }
       }
-    }).then(artifact => {
-      assert.equal(artifact.value, false);
-      assert.ok(artifact.debugString);
-    });
+    }).then(
+      _ => assert.ok(false),
+      _ => assert.ok(true));
   });
 
   it('handles driver timeout', () => {
@@ -100,9 +99,8 @@ describe('HTTP Redirect gatherer', () => {
       },
 
       _testTimeout: fastTimeout
-    }).then(artifact => {
-      assert.equal(artifact.value, false);
-      assert.ok(artifact.debugString);
-    });
+    }).then(
+      _ => assert.ok(false),
+      _ => assert.ok(true));
   });
 });

From bf526e370b023f2cdf97e3be846dba28f14e8604 Mon Sep 17 00:00:00 2001
From: Brendan Kenny <bckenny@google.com>
Date: Thu, 2 Feb 2017 13:05:01 -0800
Subject: [PATCH 08/11] delete unused and obsolete HTML gatherer

originally used as an old html minify example gather/audit - b08937c1f76997dc3fda6511222dbe2ce6fdc6d1
---
 lighthouse-core/gather/gatherers/html.js      | 42 ----------
 .../test/gather/gatherers/html-test.js        | 77 -------------------
 2 files changed, 119 deletions(-)
 delete mode 100644 lighthouse-core/gather/gatherers/html.js
 delete mode 100644 lighthouse-core/test/gather/gatherers/html-test.js

diff --git a/lighthouse-core/gather/gatherers/html.js b/lighthouse-core/gather/gatherers/html.js
deleted file mode 100644
index 59b37b68fba7..000000000000
--- a/lighthouse-core/gather/gatherers/html.js
+++ /dev/null
@@ -1,42 +0,0 @@
-/**
- * @license
- * Copyright 2016 Google Inc. All rights reserved.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-'use strict';
-
-const Gatherer = require('./gatherer');
-
-class HTML extends Gatherer {
-
-  afterPass(options) {
-    const driver = options.driver;
-
-    return driver.sendCommand('DOM.getDocument')
-        .then(result => result.root.nodeId)
-        .then(nodeId => driver.sendCommand('DOM.getOuterHTML', {
-          nodeId: nodeId
-        }))
-        .then(nodeHTML => {
-          return nodeHTML.outerHTML;
-        }).catch(_ => {
-          return {
-            value: -1,
-            debugString: 'Unable to get document HTML'
-          };
-        });
-  }
-}
-
-module.exports = HTML;
diff --git a/lighthouse-core/test/gather/gatherers/html-test.js b/lighthouse-core/test/gather/gatherers/html-test.js
deleted file mode 100644
index bc64ec220557..000000000000
--- a/lighthouse-core/test/gather/gatherers/html-test.js
+++ /dev/null
@@ -1,77 +0,0 @@
-/**
- * Copyright 2016 Google Inc. All rights reserved.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-'use strict';
-
-/* eslint-env mocha */
-
-const HTMLGather = require('../../../gather/gatherers/html');
-const assert = require('assert');
-let htmlGather;
-
-describe('HTML gatherer', () => {
-  // Reset the Gatherer before each test.
-  beforeEach(() => {
-    htmlGather = new HTMLGather();
-  });
-
-  it('returns an artifact', () => {
-    return htmlGather.afterPass({
-      driver: {
-        sendCommand(cmd) {
-          switch (cmd) {
-            case 'DOM.getDocument':
-              return Promise.resolve({
-                root: {
-                  nodeId: 1
-                }
-              });
-
-            case 'DOM.getOuterHTML':
-              return Promise.resolve({
-                outerHTML: [
-                  '<!doctype html>',
-                  '<html>',
-                  '<head><title>Doc</title></head>',
-                  '<body>Hello!</body>',
-                  '</html>'
-                ].join('\n')
-              });
-
-            default:
-              throw new Error('Unsupported command');
-          }
-        }
-      }
-    }).then(artifact => {
-      assert.ok(typeof artifact === 'string');
-      assert.ok(/<!doctype/gim.test(artifact));
-      assert.ok(/Hello/gim.test(artifact));
-    });
-  });
-
-  it('handles driver failure', () => {
-    return htmlGather.afterPass({
-      driver: {
-        sendCommand() {
-          return Promise.reject('such a fail');
-        }
-      }
-    }).then(artifact => {
-      assert.equal(artifact.value, -1);
-      assert.ok(artifact.debugString);
-    });
-  });
-});

From 950bdc2da4aff38708ca88953a86e51be2f98e10 Mon Sep 17 00:00:00 2001
From: Brendan Kenny <bckenny@google.com>
Date: Thu, 2 Feb 2017 13:12:47 -0800
Subject: [PATCH 09/11] update WithoutJavascript gatherer to use Errors for
 errors

---
 lighthouse-core/audits/without-javascript.js  |  7 -----
 .../gatherers/html-without-javascript.js      |  8 +-----
 .../test/audits/without-javascript-test.js    | 26 -----------------
 .../gatherers/html-without-javascript-test.js | 28 +++++--------------
 4 files changed, 8 insertions(+), 61 deletions(-)

diff --git a/lighthouse-core/audits/without-javascript.js b/lighthouse-core/audits/without-javascript.js
index 0fd3200483ba..7326b4c4115b 100644
--- a/lighthouse-core/audits/without-javascript.js
+++ b/lighthouse-core/audits/without-javascript.js
@@ -41,13 +41,6 @@ class WithoutJavaScript extends Audit {
    */
   static audit(artifacts) {
     const artifact = artifacts.HTMLWithoutJavaScript;
-    if (typeof artifact.value !== 'string') {
-      return WithoutJavaScript.generateAuditResult({
-        rawValue: -1,
-        debugString: artifact.debugString ||
-            'HTMLWithoutJavaScript gatherer did not complete successfully'
-      });
-    }
 
     if (artifact.value.trim() === '') {
       return WithoutJavaScript.generateAuditResult({
diff --git a/lighthouse-core/gather/gatherers/html-without-javascript.js b/lighthouse-core/gather/gatherers/html-without-javascript.js
index 738d2ef9c0d1..5908e309256d 100644
--- a/lighthouse-core/gather/gatherers/html-without-javascript.js
+++ b/lighthouse-core/gather/gatherers/html-without-javascript.js
@@ -44,18 +44,12 @@ class HTMLWithoutJavaScript extends Gatherer {
     return options.driver.evaluateAsync(`(${getBodyText.toString()}())`)
       .then(result => {
         if (typeof result !== 'string') {
-          throw new Error('result was not a string');
+          throw new Error('document body innerText returned by protocol was not a string');
         }
 
         return {
           value: result
         };
-      })
-      .catch(err => {
-        return {
-          value: -1,
-          debugString: `Unable to get document body innerText: ${err.message}`
-        };
       });
   }
 }
diff --git a/lighthouse-core/test/audits/without-javascript-test.js b/lighthouse-core/test/audits/without-javascript-test.js
index ee0668d24c2d..ad1be40c9239 100644
--- a/lighthouse-core/test/audits/without-javascript-test.js
+++ b/lighthouse-core/test/audits/without-javascript-test.js
@@ -21,32 +21,6 @@ const withoutJsAudit = require('../../audits/without-javascript.js');
 const assert = require('assert');
 
 describe('Progressive Enhancement: without javascript audit', () => {
-  it('passes on the error when there was a driver error', () => {
-    const debugString = 'Unusual error string';
-    const artifacts = {
-      HTMLWithoutJavaScript: {
-        value: -1,
-        debugString
-      }
-    };
-
-    const result = withoutJsAudit.audit(artifacts);
-    assert.equal(result.score, -1);
-    assert.equal(result.debugString, debugString);
-  });
-
-  it('does not error on non-string input', () => {
-    const artifacts = {
-      HTMLWithoutJavaScript: {
-        value: {}
-      }
-    };
-
-    const result = withoutJsAudit.audit(artifacts);
-    assert.equal(result.score, -1);
-    assert.ok(result.debugString);
-  });
-
   it('fails when the js-less body is empty', () => {
     const artifacts = {
       HTMLWithoutJavaScript: {
diff --git a/lighthouse-core/test/gather/gatherers/html-without-javascript-test.js b/lighthouse-core/test/gather/gatherers/html-without-javascript-test.js
index 1db55d7332dc..cda1f3c701d7 100644
--- a/lighthouse-core/test/gather/gatherers/html-without-javascript-test.js
+++ b/lighthouse-core/test/gather/gatherers/html-without-javascript-test.js
@@ -51,41 +51,27 @@ describe('HTML without JavaScript gatherer', () => {
   });
 
   it('returns an artifact', () => {
+    const innerText = 'Hello!';
     return htmlWithoutJavaScriptGather.afterPass({
       driver: {
         evaluateAsync() {
-          return Promise.resolve('Hello!');
+          return Promise.resolve(innerText);
         }
       }
     }).then(artifact => {
-      assert.ok(typeof artifact.value === 'string');
-      assert.ok(/Hello/gim.test(artifact.value));
+      assert.strictEqual(artifact.value, innerText);
     });
   });
 
-  it('handles driver returning non-string', () => {
+  it('throws an error when driver returns a non-string', () => {
     return htmlWithoutJavaScriptGather.afterPass({
       driver: {
         evaluateAsync() {
           return Promise.resolve(null);
         }
       }
-    }).then(artifact => {
-      assert.equal(artifact.value, -1);
-      assert.ok(artifact.debugString);
-    });
-  });
-
-  it('handles driver failure', () => {
-    return htmlWithoutJavaScriptGather.afterPass({
-      driver: {
-        evaluateAsync() {
-          return Promise.reject(new Error('such a fail'));
-        }
-      }
-    }).then(artifact => {
-      assert.equal(artifact.value, -1);
-      assert.ok(/such a fail/i.test(artifact.debugString));
-    });
+    }).then(
+      _ => assert.ok(false),
+      _ => assert.ok(true));
   });
 });

From f9da4357f06d81e479644f8983e882225ef054fd Mon Sep 17 00:00:00 2001
From: Brendan Kenny <bckenny@google.com>
Date: Thu, 2 Feb 2017 15:09:49 -0800
Subject: [PATCH 10/11] update ChromeConsoleMessages gatherer to use Errors for
 errors

---
 lighthouse-core/audits/deprecations.js               |  4 ----
 .../gather/gatherers/chrome-console-messages.js      |  8 +-------
 lighthouse-core/test/audits/deprecations-test.js     | 12 ------------
 3 files changed, 1 insertion(+), 23 deletions(-)

diff --git a/lighthouse-core/audits/deprecations.js b/lighthouse-core/audits/deprecations.js
index fd234562a335..154168124d34 100644
--- a/lighthouse-core/audits/deprecations.js
+++ b/lighthouse-core/audits/deprecations.js
@@ -45,10 +45,6 @@ class Deprecations extends Audit {
    * @return {!AuditResult}
    */
   static audit(artifacts) {
-    if (artifacts.ChromeConsoleMessages.rawValue === -1) {
-      return Deprecations.generateAuditResult(artifacts.ChromeConsoleMessages);
-    }
-
     const entries = artifacts.ChromeConsoleMessages;
 
     const deprecations = entries.filter(log => log.entry.source === 'deprecation')
diff --git a/lighthouse-core/gather/gatherers/chrome-console-messages.js b/lighthouse-core/gather/gatherers/chrome-console-messages.js
index 84097cabb76d..2f1f60abc646 100644
--- a/lighthouse-core/gather/gatherers/chrome-console-messages.js
+++ b/lighthouse-core/gather/gatherers/chrome-console-messages.js
@@ -43,13 +43,7 @@ class ChromeConsoleMessages extends Gatherer {
   afterPass(options) {
     options.driver.off('Log.entryAdded', this._onConsoleEntryAdded);
     return options.driver.sendCommand('Log.disable')
-        .then(_ => this._logEntries)
-        .catch(err => {
-          return {
-            rawValue: -1,
-            debugString: err.message
-          };
-        });
+        .then(_ => this._logEntries);
   }
 }
 
diff --git a/lighthouse-core/test/audits/deprecations-test.js b/lighthouse-core/test/audits/deprecations-test.js
index 6d9ed31ec8bc..54bcfb753ddc 100644
--- a/lighthouse-core/test/audits/deprecations-test.js
+++ b/lighthouse-core/test/audits/deprecations-test.js
@@ -22,18 +22,6 @@ const assert = require('assert');
 /* eslint-env mocha */
 
 describe('Console deprecations audit', () => {
-  it('fails when gather fails', () => {
-    const debugString = 'the uniquest debug string';
-    const auditResult = DeprecationsAudit.audit({
-      ChromeConsoleMessages: {
-        rawValue: -1,
-        debugString
-      }
-    });
-    assert.equal(auditResult.rawValue, -1);
-    assert.strictEqual(auditResult.debugString, debugString);
-  });
-
   it('passes when no console messages were found', () => {
     const auditResult = DeprecationsAudit.audit({
       ChromeConsoleMessages: []

From a9e431d75d26881af8e3f89f624e79e8ebe3f8f4 Mon Sep 17 00:00:00 2001
From: Brendan Kenny <bckenny@google.com>
Date: Thu, 2 Feb 2017 15:42:36 -0800
Subject: [PATCH 11/11] update Accessibility gatherer to use Errors for errors

---
 .../audits/accessibility/axe-audit.js         |  2 +-
 .../gather/gatherers/accessibility.js         | 32 +++++--------
 .../accessibility/aria-allowed-attr-test.js   | 11 -----
 .../accessibility/aria-required-attr-test.js  | 12 -----
 .../accessibility/aria-valid-attr-test.js     | 12 -----
 .../aria-valid-attr-value-test.js             | 11 -----
 .../accessibility/color-contrast-test.js      | 12 -----
 .../audits/accessibility/image-alt-test.js    | 11 -----
 .../test/audits/accessibility/label-test.js   | 11 -----
 .../audits/accessibility/tabindex-test.js     | 11 -----
 .../gather/gatherers/accessibility-test.js    | 45 +++++++------------
 11 files changed, 27 insertions(+), 143 deletions(-)

diff --git a/lighthouse-core/audits/accessibility/axe-audit.js b/lighthouse-core/audits/accessibility/axe-audit.js
index 5ec6617d951d..55e46a862557 100644
--- a/lighthouse-core/audits/accessibility/axe-audit.js
+++ b/lighthouse-core/audits/accessibility/axe-audit.js
@@ -32,7 +32,7 @@ class AxeAudit extends Audit {
    * @return {!AuditResult}
    */
   static audit(artifacts) {
-    const violations = artifacts.Accessibility.violations || [];
+    const violations = artifacts.Accessibility.violations;
     const rule = violations.find(result => result.id === this.meta.name);
 
     return this.generateAuditResult({
diff --git a/lighthouse-core/gather/gatherers/accessibility.js b/lighthouse-core/gather/gatherers/accessibility.js
index dbae06fb98c2..5e9d2c6c79f4 100644
--- a/lighthouse-core/gather/gatherers/accessibility.js
+++ b/lighthouse-core/gather/gatherers/accessibility.js
@@ -47,14 +47,10 @@ function runA11yChecks() {
 }
 
 class Accessibility extends Gatherer {
-  static _errorAccessibility(errorString) {
-    return {
-      raw: undefined,
-      value: undefined,
-      debugString: errorString
-    };
-  }
-
+  /**
+   * @param {!Object} options
+   * @return {!Promise<{violations: !Array}>}
+   */
   afterPass(options) {
     const driver = options.driver;
     const expression = `(function () {
@@ -63,20 +59,14 @@ class Accessibility extends Gatherer {
     })()`;
 
     return driver
-        .evaluateAsync(expression)
-        .then(returnedValue => {
-          if (!returnedValue) {
-            return Accessibility._errorAccessibility('Unable to parse axe results');
-          }
-
-          if (returnedValue.error) {
-            return Accessibility._errorAccessibility(returnedValue.error);
-          }
+      .evaluateAsync(expression)
+      .then(returnedValue => {
+        if (!returnedValue || !Array.isArray(returnedValue.violations)) {
+          throw new Error('Unable to parse axe results' + returnedValue);
+        }
 
-          return returnedValue;
-        }, _ => {
-          return Accessibility._errorAccessibility('Axe results timed out');
-        });
+        return returnedValue;
+      });
   }
 }
 
diff --git a/lighthouse-core/test/audits/accessibility/aria-allowed-attr-test.js b/lighthouse-core/test/audits/accessibility/aria-allowed-attr-test.js
index 44d326460443..1fe78d5b8d28 100644
--- a/lighthouse-core/test/audits/accessibility/aria-allowed-attr-test.js
+++ b/lighthouse-core/test/audits/accessibility/aria-allowed-attr-test.js
@@ -53,15 +53,4 @@ describe('Accessibility: aria-allowed-attr audit', () => {
     assert.equal(output.rawValue, false);
     assert.equal(output.displayValue, '');
   });
-
-  it('doesn\'t throw an error when violations is undefined', () => {
-    const artifacts = {
-      Accessibility: {
-        violations: undefined
-      }
-    };
-
-    const output = Audit.audit(artifacts);
-    assert.equal(output.description, 'Element aria-* attributes are allowed for this role');
-  });
 });
diff --git a/lighthouse-core/test/audits/accessibility/aria-required-attr-test.js b/lighthouse-core/test/audits/accessibility/aria-required-attr-test.js
index c729a65319ba..57ca0455873c 100644
--- a/lighthouse-core/test/audits/accessibility/aria-required-attr-test.js
+++ b/lighthouse-core/test/audits/accessibility/aria-required-attr-test.js
@@ -53,16 +53,4 @@ describe('Accessibility: aria-required-attr audit', () => {
     assert.equal(output.rawValue, false);
     assert.equal(output.displayValue, '');
   });
-
-  it('doesn\'t throw an error when violations is undefined', () => {
-    const artifacts = {
-      Accessibility: {
-        violations: undefined
-      }
-    };
-
-    const output = Audit.audit(artifacts);
-    assert.equal(output.description,
-        'Elements with ARIA roles have the required aria-* attributes');
-  });
 });
diff --git a/lighthouse-core/test/audits/accessibility/aria-valid-attr-test.js b/lighthouse-core/test/audits/accessibility/aria-valid-attr-test.js
index 5daea6f68270..a3753350348a 100644
--- a/lighthouse-core/test/audits/accessibility/aria-valid-attr-test.js
+++ b/lighthouse-core/test/audits/accessibility/aria-valid-attr-test.js
@@ -53,16 +53,4 @@ describe('Accessibility: aria-valid-attr audit', () => {
     assert.equal(output.rawValue, false);
     assert.equal(output.displayValue, '');
   });
-
-  it('doesn\'t throw an error when violations is undefined', () => {
-    const artifacts = {
-      Accessibility: {
-        violations: undefined
-      }
-    };
-
-    const output = Audit.audit(artifacts);
-    assert.equal(output.description,
-        'Element aria-* attributes are valid and not misspelled or non-existent.');
-  });
 });
diff --git a/lighthouse-core/test/audits/accessibility/aria-valid-attr-value-test.js b/lighthouse-core/test/audits/accessibility/aria-valid-attr-value-test.js
index 1c55db1ae22b..88f052883456 100644
--- a/lighthouse-core/test/audits/accessibility/aria-valid-attr-value-test.js
+++ b/lighthouse-core/test/audits/accessibility/aria-valid-attr-value-test.js
@@ -53,15 +53,4 @@ describe('Accessibility: aria-valid-attr-value audit', () => {
     assert.equal(output.rawValue, false);
     assert.equal(output.displayValue, '');
   });
-
-  it('doesn\'t throw an error when violations is undefined', () => {
-    const artifacts = {
-      Accessibility: {
-        violations: undefined
-      }
-    };
-
-    const output = Audit.audit(artifacts);
-    assert.equal(output.description, 'Element aria-* attributes have valid values');
-  });
 });
diff --git a/lighthouse-core/test/audits/accessibility/color-contrast-test.js b/lighthouse-core/test/audits/accessibility/color-contrast-test.js
index fe3c1cba9755..618286d477c6 100644
--- a/lighthouse-core/test/audits/accessibility/color-contrast-test.js
+++ b/lighthouse-core/test/audits/accessibility/color-contrast-test.js
@@ -53,16 +53,4 @@ describe('Accessibility: color-contrast audit', () => {
     assert.equal(output.rawValue, false);
     assert.equal(output.displayValue, '');
   });
-
-  it('doesn\'t throw an error when violations is undefined', () => {
-    const artifacts = {
-      Accessibility: {
-        violations: undefined
-      }
-    };
-
-    const output = Audit.audit(artifacts);
-    assert.equal(output.description,
-        'Background and foreground colors have a sufficient contrast ratio');
-  });
 });
diff --git a/lighthouse-core/test/audits/accessibility/image-alt-test.js b/lighthouse-core/test/audits/accessibility/image-alt-test.js
index 9a9108449d46..e8e7f71789a1 100644
--- a/lighthouse-core/test/audits/accessibility/image-alt-test.js
+++ b/lighthouse-core/test/audits/accessibility/image-alt-test.js
@@ -53,15 +53,4 @@ describe('Accessibility: image-alt audit', () => {
     assert.equal(output.rawValue, false);
     assert.equal(output.displayValue, '');
   });
-
-  it('doesn\'t throw an error when violations is undefined', () => {
-    const artifacts = {
-      Accessibility: {
-        violations: undefined
-      }
-    };
-
-    const output = Audit.audit(artifacts);
-    assert.equal(output.description, 'Every image element has an alt attribute');
-  });
 });
diff --git a/lighthouse-core/test/audits/accessibility/label-test.js b/lighthouse-core/test/audits/accessibility/label-test.js
index 235d9cad29aa..3d4f9aa98b73 100644
--- a/lighthouse-core/test/audits/accessibility/label-test.js
+++ b/lighthouse-core/test/audits/accessibility/label-test.js
@@ -53,15 +53,4 @@ describe('Accessibility: label audit', () => {
     assert.equal(output.rawValue, false);
     assert.equal(output.displayValue, '');
   });
-
-  it('doesn\'t throw an error when violations is undefined', () => {
-    const artifacts = {
-      Accessibility: {
-        violations: undefined
-      }
-    };
-
-    const output = Audit.audit(artifacts);
-    assert.equal(output.description, 'Every form element has a label');
-  });
 });
diff --git a/lighthouse-core/test/audits/accessibility/tabindex-test.js b/lighthouse-core/test/audits/accessibility/tabindex-test.js
index 4aee4d7a45e5..3772ddde4f00 100644
--- a/lighthouse-core/test/audits/accessibility/tabindex-test.js
+++ b/lighthouse-core/test/audits/accessibility/tabindex-test.js
@@ -53,15 +53,4 @@ describe('Accessibility: tabindex audit', () => {
     assert.equal(output.rawValue, false);
     assert.equal(output.displayValue, '');
   });
-
-  it('doesn\'t throw an error when violations is undefined', () => {
-    const artifacts = {
-      Accessibility: {
-        violations: undefined
-      }
-    };
-
-    const output = Audit.audit(artifacts);
-    assert.equal(output.description, 'No element has a `tabindex` attribute greater than 0');
-  });
 });
diff --git a/lighthouse-core/test/gather/gatherers/accessibility-test.js b/lighthouse-core/test/gather/gatherers/accessibility-test.js
index 3e32ba069f3c..b05f1fb2b341 100644
--- a/lighthouse-core/test/gather/gatherers/accessibility-test.js
+++ b/lighthouse-core/test/gather/gatherers/accessibility-test.js
@@ -27,57 +27,42 @@ describe('Accessibility gatherer', () => {
     accessibilityGather = new AccessibilityGather();
   });
 
-  it('fails gracefully', () => {
+  it('fails if nothing is returned', () => {
     return accessibilityGather.afterPass({
       driver: {
         evaluateAsync() {
           return Promise.resolve();
         }
       }
-    }).then(artifact => {
-      assert.ok(typeof artifact === 'object');
-    });
+    }).then(
+      _ => assert.ok(false),
+      _ => assert.ok(true));
   });
 
-  it('handles driver failure', () => {
-    return accessibilityGather.afterPass({
-      driver: {
-        evaluateAsync() {
-          return Promise.reject('such a fail');
-        }
-      }
-    }).then(artifact => {
-      assert.ok(artifact.debugString);
-    });
-  });
-
-  it('propagates error retrieving the results', () => {
-    const error = 'There was an error.';
+  it('fails if result has no violations array', () => {
     return accessibilityGather.afterPass({
       driver: {
         evaluateAsync() {
           return Promise.resolve({
-            error
+            url: 'https://example.com'
           });
         }
       }
-    }).then(artifact => {
-      assert.ok(artifact.debugString === error);
-    });
+    }).then(
+      _ => assert.ok(false),
+      _ => assert.ok(true));
   });
 
-  it('creates an object for valid results', () => {
+  it('propagates error retrieving the results', () => {
+    const error = 'There was an error.';
     return accessibilityGather.afterPass({
       driver: {
         evaluateAsync() {
-          return Promise.resolve({
-            name: 'a11y'
-          });
+          return Promise.reject(new Error(error));
         }
       }
-    }).then(artifact => {
-      assert.ok(typeof artifact === 'object');
-      assert.equal(artifact.name, 'a11y');
-    });
+    }).then(
+      _ => assert.ok(false),
+      err => assert.ok(err.message.includes(error)));
   });
 });