DevTools: Support timeline JS sampling for all threads.

Source/devtools/front_end/timeline/TimelineJSProfile.js

 // Copyright 2014 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.
 
 
 WebInspector.TimelineJSProfileProcessor = { };
 
 /**
- * @param {!WebInspector.TracingTimelineModel} timelineModel
  * @param {!ProfilerAgent.CPUProfile} jsProfile
+ * @param {!WebInspector.TracingModel.Thread} thread
  * @return {!Array.<!WebInspector.TracingModel.Event>}
  */
-WebInspector.TimelineJSProfileProcessor.generateTracingEventsFromCpuProfile = function(timelineModel, jsProfile)
+WebInspector.TimelineJSProfileProcessor.generateTracingEventsFromCpuProfile = function(jsProfile, thread)
 {
     if (!jsProfile.samples)
         return [];
     var jsProfileModel = new WebInspector.CPUProfileDataModel(jsProfile);
     var idleNode = jsProfileModel.idleNode;
     var programNode = jsProfileModel.programNode;
     var gcNode = jsProfileModel.gcNode;
     var samples = jsProfileModel.samples;
     var timestamps = jsProfileModel.timestamps;
     var jsEvents = [];
-    var mainThread = timelineModel.mainThreadEvents()[0].thread;
     for (var i = 0; i < samples.length; ++i) {
         var node = jsProfileModel.nodeByIndex(i);
         if (node === programNode || node === gcNode || node === idleNode)
             continue;
         var stackTrace = node._stackTraceArray;
         if (!stackTrace) {
             stackTrace = /** @type {!ConsoleAgent.StackTrace} */ (new Array(node.depth + 1));
             node._stackTraceArray = stackTrace;
             for (var j = 0; node.parent; node = node.parent)
                 stackTrace[j++] = /** @type {!ConsoleAgent.CallFrame} */ (node);
         }
         var jsEvent = new WebInspector.TracingModel.Event(WebInspector.TracingModel.DevToolsMetadataEventCategory, WebInspector.TracingTimelineModel.RecordType.JSSample,
-            WebInspector.TracingModel.Phase.Instant, timestamps[i], mainThread);
+            WebInspector.TracingModel.Phase.Instant, timestamps[i], thread);
         jsEvent.stackTrace = stackTrace;
         jsEvents.push(jsEvent);
     }
     return jsEvents;
 }