core: Support traces with TracingStartedInBrowser event

Since version 67 Chrome uses a new schema to describe page frame tree. The tree is encoded within TracingStartedInBrowser trace event. The patch makes lighthouse to support the new event. Legacy TracingStartedInPage event is going to the removed soon.
GoogleChrome · Jun 4, 2018 · 5b1793d · 5b1793d
1 parent d63f491
commit 5b1793d
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Showing 3 changed files with 5 additions and 8 deletions.
diff --git a/lighthouse-core/gather/computed/trace-of-tab.js b/lighthouse-core/gather/computed/trace-of-tab.js
@@ -44,9 +44,9 @@ class TraceOfTab extends ComputedArtifact {
     const keyEvents = trace.traceEvents
       .filter(e => {
         return e.cat.includes('blink.user_timing') ||
-          e.cat.includes('loading') ||
-          e.cat.includes('devtools.timeline') ||
-          e.cat === '__metadata';
+            e.cat.includes('loading') ||
+            e.cat.includes('devtools.timeline') ||
+            e.cat === '__metadata';
       })
       // @ts-ignore - stableSort added to Array by WebInspector.
       .stableSort((event0, event1) => event0.ts - event1.ts);
@@ -55,10 +55,9 @@ class TraceOfTab extends ComputedArtifact {
     /** @type {LH.TraceEvent|undefined} */
     let startedInPageEvt;
     const startedInBrowserEvt = keyEvents.find(e => e.name === 'TracingStartedInBrowser');
-    // `persistentIds` is a signal that the frame data will be attached, prefer it when available.
     if (startedInBrowserEvt && startedInBrowserEvt.args.data &&
-        startedInBrowserEvt.args.data.persistentIds) {
-      const mainFrame = (startedInBrowserEvt.args.data.frames || []).find(frame => !frame.parent);
+        startedInBrowserEvt.args.data.frames) {
+      const mainFrame = startedInBrowserEvt.args.data.frames.find(frame => !frame.parent);
       const pid = mainFrame && mainFrame.processId;
       const threadNameEvt = keyEvents.find(e => e.pid === pid && e.ph === 'M' &&
         e.cat === '__metadata' && e.name === 'thread_name' && e.args.name === 'CrRendererMain');

diff --git a/lighthouse-core/test/gather/computed/trace-of-tab-test.js b/lighthouse-core/test/gather/computed/trace-of-tab-test.js
@@ -123,7 +123,6 @@ describe('Trace of Tab computed artifact:', () => {
         'name': 'TracingStartedInBrowser',
         'args': {'data': {
           'frameTreeNodeId': 1,
-          'persistentIds': true,
           'frames': [{
             'frame': 'B192D1F3355A6F961EC8F0B01623C1FB',
             'url': 'http://www.example.com/',

diff --git a/typings/externs.d.ts b/typings/externs.d.ts
@@ -138,7 +138,6 @@ declare global {
       args: {
         data?: {
           name?: string;
-          persistentIds?: boolean;
           frames?: {
             frame: string;
             parent?: string;