DevTools: Collect JS samples when recording timeline

Source/devtools/front_end/sdk/CPUProfileDataModel.js

Index: Source/devtools/front_end/sdk/CPUProfileDataModel.js
diff --git a/Source/devtools/front_end/sdk/CPUProfileDataModel.js b/Source/devtools/front_end/sdk/CPUProfileDataModel.js
index bc592d4a583f1e3af3121d64e28ffb71908e2e82..846b50df795c3020091b65aae2dbc85b15583171 100644
--- a/Source/devtools/front_end/sdk/CPUProfileDataModel.js
+++ b/Source/devtools/front_end/sdk/CPUProfileDataModel.js
@@ -293,5 +293,15 @@ WebInspector.CPUProfileDataModel.prototype = {
             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]];
     }
+
 }