remove redundant gatherer lifecycle methods

lighthouse-core/gather/drivers/driver.js

@@ -247,7 +247,7 @@ class Driver {
           return resolve();
         }
 
-        this.on('Page.loadEventFired', response => {
+        this.once('Page.loadEventFired', response => {
           setTimeout(_ => {
             resolve(response);
           }, this.PAUSE_AFTER_LOAD);

lighthouse-core/gather/gather-runner.js

@@ -51,10 +51,9 @@ class GatherRunner {
     });
   }
 
-  static setup(options) {
+  static setupPass(options) {
     const driver = options.driver;
     const config = options.config;
-    const gatherers = config.gatherers;
     let pass = Promise.resolve();
 
     if (config.trace) {
@@ -65,9 +64,7 @@ class GatherRunner {
       pass = pass.then(_ => driver.beginNetworkCollect());
     }
 
-    return gatherers.reduce((chain, gatherer) => {
-      return chain.then(_ => gatherer.setup(options));
-    }, pass);
+    return pass;
   }
 
   static beforePass(options) {
@@ -160,14 +157,6 @@ class GatherRunner {
         .then(_ => loadData);
   }
 
-  static tearDown(options) {
-    const config = options.config;
-    const gatherers = config.gatherers;
-    return gatherers.reduce((chain, gatherer) => {
-      return chain.then(_ => gatherer.tearDown(options));
-    }, Promise.resolve());
-  }
-
   static run(passes, options) {
     const driver = options.driver;
     const tracingData = {traces: {}};
@@ -200,16 +189,15 @@ class GatherRunner {
         return passes.reduce((chain, config) => {
           const runOptions = Object.assign({}, options, {config});
           return chain
-              .then(_ => this.setup(runOptions))
+              .then(_ => this.setupPass(runOptions))
               .then(_ => this.beforePass(runOptions))
               .then(_ => this.pass(runOptions))
               .then(_ => this.afterPass(runOptions))
               .then(loadData => {
                 // Merge pass trace and network data into tracingData.
                 config.trace && Object.assign(tracingData.traces, loadData.traces);
                 config.network && (tracingData.networkRecords = loadData.networkRecords);
-              })
-              .then(_ => this.tearDown(runOptions));
+              });
         }, Promise.resolve());
       })
       .then(_ => {

lighthouse-core/gather/gatherers/gatherer.js

@@ -34,15 +34,27 @@ class Gatherer {
 
   /* eslint-disable no-unused-vars */
 
-  setup(options) { }
-
+  /**
+   * Called before navigation to target url.
+   * @param {!Object} options
+   */
   beforePass(options) { }
 
+  /**
+   * Called after target page is loaded. If a trace is enabled for this pass,
+   * the trace is still being recorded.
+   * @param {!Object} options
+   */
   pass(options) { }
 
-  afterPass(options) { }
-
-  tearDown(options) { }
+  /**
+   * Called after target page is loaded, all gatherer `pass` methods have been
+   * executed, and — if generated in this pass — the trace is ended. The trace
+   * and record of network activity are provided in `loadData`.
+   * @param {!Object} options
+   * @param {{networkRecords: !Array, traceEvents: !Array} loadData
+   */
+  afterPass(options, loadData) { }
 
   /* eslint-enable no-unused-vars */
 

lighthouse-core/test/gather/gather-runner.js

@@ -33,7 +33,7 @@ class TestGatherer extends Gatherer {
     return 'test';
   }
 
-  setup() {
+  pass() {
     this.called = true;
   }
 }
@@ -132,12 +132,10 @@ describe('GatherRunner', function() {
 
     const config = {
       trace: true,
-      gatherers: [{
-        setup() {}
-      }]
+      gatherers: [{}]
     };
 
-    return GatherRunner.setup({driver, config}).then(_ => {
+    return GatherRunner.setupPass({driver, config}).then(_ => {
       assert.equal(calledTrace, true);
     });
   });
@@ -195,12 +193,10 @@ describe('GatherRunner', function() {
 
     const config = {
       network: true,
-      gatherers: [{
-        setup() {}
-      }]
+      gatherers: [{}]
     };
 
-    return GatherRunner.setup({driver, config}).then(_ => {
+    return GatherRunner.setupPass({driver, config}).then(_ => {
       assert.equal(calledNetworkCollect, true);
     });
   });