DevTools: Resume targets *after* stopping timeline recording.

third_party/WebKit/Source/devtools/front_end/timeline/TimelineController.js

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @constructor
  * @param {!WebInspector.TimelineLifecycleDelegate} delegate
  * @param {!WebInspector.TracingModel} tracingModel
  * @implements {WebInspector.TargetManager.Observer}
  * @implements {WebInspector.TracingManagerClient}
@@ skipping 52 matching lines @@
         }
         if (captureFilmStrip)
             categoriesArray.push(disabledByDefault("devtools.screenshot"));
 
         var categories = categoriesArray.join(",");
         this._startRecordingWithCategories(categories, enableJSSampling);
     },
 
     stopRecording: function()
     {
+        this._allProfilesStoppedPromise = this._stopProfilingOnAllTargets();
+        var mainTarget = WebInspector.targetManager.mainTarget();
+        if (mainTarget)
+            mainTarget.tracingManager.stop();
         WebInspector.targetManager.resumeAllTargets();
-        this._allProfilesStoppedPromise = this._stopProfilingOnAllTargets();
-        if (this._targets[0])
-            this._targets[0].tracingManager.stop();
         this._delegate.loadingStarted();
     },
 
     /**
      * @override
      * @param {!WebInspector.Target} target
      */
     targetAdded: function(target)
     {
         this._targets.push(target);
         if (this._profiling)
             this._startProfilingOnTarget(target);
     },
 
     /**
      * @override
      * @param {!WebInspector.Target} target
      */
     targetRemoved: function(target)
     {
         this._targets.remove(target, true);
         // FIXME: We'd like to stop profiling on the target and retrieve a profile
         // but it's too late. Backend connection is closed.
+        if (this._profiling)
+            WebInspector.console.log(WebInspector.UIString("A target is disconnected while profiling. Its profile will not be retrieved."));

[pfeldman, 2016/03/17 00:34:31]

Don't output this message - it jumps at the user in the middle of the recording.
Surface it upon stop instead.

"One of the targets (worker?) was disconnected while profiling. Its profile was
not captured."

[alph, 2016/03/17 01:10:08]

Done.

     },
 
     /**
      * @param {!WebInspector.Target} target
      * @return {!Promise}
      */
     _startProfilingOnTarget: function(target)
     {
         return target.profilerAgent().start();
     },
 
     /**
      * @return {!Promise}
      */
     _startProfilingOnAllTargets: function()
     {
         var intervalUs = WebInspector.moduleSetting("highResolutionCpuProfiling").get() ? 100 : 1000;
-        this._targets[0].profilerAgent().setSamplingInterval(intervalUs);
+        var mainTarget = WebInspector.targetManager.mainTarget();
+        if (mainTarget)
+            mainTarget.profilerAgent().setSamplingInterval(intervalUs);
         this._profiling = true;
         return Promise.all(this._targets.map(this._startProfilingOnTarget));
     },
 
     /**
      * @param {!WebInspector.Target} target
      * @return {!Promise}
      */
     _stopProfilingOnTarget: function(target)
     {
-        /**
-         * @param {?Protocol.Error} error
-         * @param {?ProfilerAgent.CPUProfile} profile
-         * @return {?ProfilerAgent.CPUProfile}
-         */
-        function extractProfile(error, profile)
-        {
-            return !error && profile ? profile : null;
-        }
-        return target.profilerAgent().stop(extractProfile).then(this._addCpuProfile.bind(this, target.id()));
+        return target.profilerAgent().stop((error, profile) => !error && profile ? profile : null)
+            .then(this._addCpuProfile.bind(this, target.id()));
     },
 
     /**
      * @return {!Promise}
      */
     _stopProfilingOnAllTargets: function()
     {
         var targets = this._profiling ? this._targets : [];
         this._profiling = false;
         return Promise.all(targets.map(this._stopProfilingOnTarget, this));
     },
 
     /**
      * @param {string} categories
      * @param {boolean=} enableJSSampling
      * @param {function(?string)=} callback
      */
     _startRecordingWithCategories: function(categories, enableJSSampling, callback)
     {
         if (!this._targets.length)
             return;
         WebInspector.targetManager.suspendAllTargets();
         var profilingStartedPromise = enableJSSampling && !Runtime.experiments.isEnabled("timelineTracingJSProfile") ?
             this._startProfilingOnAllTargets() : Promise.resolve();
         var samplingFrequencyHz = WebInspector.moduleSetting("highResolutionCpuProfiling").get() ? 10000 : 1000;
         var options = "sampling-frequency=" + samplingFrequencyHz;
-        var mainTarget = this._targets[0];
+        var mainTarget = WebInspector.targetManager.mainTarget();
         var tracingManager = mainTarget.tracingManager;
         mainTarget.resourceTreeModel.suspendReload();
         profilingStartedPromise.then(tracingManager.start.bind(tracingManager, this, categories, options, onTraceStarted));
         /**
          * @param {?string} error
          */
         function onTraceStarted(error)
         {
             mainTarget.resourceTreeModel.resumeReload();
             if (callback)
@@ skipping 65 matching lines @@
         if (!this._cpuProfiles)
             return;
 
         var metadataEventTypes = WebInspector.TimelineModel.DevToolsMetadataEvent;
         var metadataEvents = this._tracingModel.devToolsMetadataEvents();
         var mainMetaEvent = metadataEvents.filter(event => event.name === metadataEventTypes.TracingStartedInPage).peekLast();
         if (!mainMetaEvent)
             return;
 
         var pid = mainMetaEvent.thread.process().id();
-        var mainTarget = this._targets[0];
+        var mainTarget = WebInspector.targetManager.mainTarget();
         var mainCpuProfile = this._cpuProfiles.get(mainTarget.id());
         this._injectCpuProfileEvent(pid, mainMetaEvent.thread.id(), mainCpuProfile);
 
         var workerMetaEvents = metadataEvents.filter(event => event.name === metadataEventTypes.TracingSessionIdForWorker);
         for (var metaEvent of workerMetaEvents) {
             var workerId = metaEvent.args["data"]["workerId"];
             var target = mainTarget.workerManager ? mainTarget.workerManager.targetByWorkerId(workerId) : null;
             if (!target)
                 continue;
             var cpuProfile = this._cpuProfiles.get(target.id());
@@ skipping 26 matching lines @@
      */
     _addCpuProfile: function(targetId, cpuProfile)
     {
         if (!cpuProfile)
             return;
         if (!this._cpuProfiles)
             this._cpuProfiles = new Map();
         this._cpuProfiles.set(targetId, cpuProfile);
     }
 }