DevTools: Collect JS samples when recording timeline

Source/devtools/front_end/sdk/CPUProfileDataModel.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.
 
 
 /**
  * @constructor
  * @param {!ProfilerAgent.CPUProfile} profile
  */
 WebInspector.CPUProfileDataModel = function(profile)
@@ skipping 275 matching lines @@
             --stackTop;
         }
 
         for (var node = idToNode[prevId]; node.parent; node = node.parent) {
             var start = stackStartTimes[stackTop];
             var duration = sampleTime - start;
             stackChildrenDuration[stackTop - 1] += duration;
             closeFrameCallback(node.depth, node, start, duration, duration - stackChildrenDuration[stackTop]);
             --stackTop;
         }
+    },
+
+    /**
+     * @param {number} index
+     * @return {!ProfilerAgent.CPUProfileNode}
+     */
+    nodeByIndex: function(index)
+    {
+        return this._idToNode[this.samples[index]];
     }
+
 }