Timeline: fill frames according to CPU time spent per event category

Source/devtools/front_end/timeline/TracingModel.js

Index: Source/devtools/front_end/timeline/TracingModel.js
diff --git a/Source/devtools/front_end/timeline/TracingModel.js b/Source/devtools/front_end/timeline/TracingModel.js
index 9dd7a0ec899249d8788659fee97459b25fc39efb..9265df8f85ed53dc19a50f0c38eebfd2e0098db3 100644
--- a/Source/devtools/front_end/timeline/TracingModel.js
+++ b/Source/devtools/front_end/timeline/TracingModel.js
@@ -120,19 +120,23 @@ WebInspector.TracingModel.prototype = {
     },
 
     /**
-     * @param {string} sessionId
+     * @return {?string}
      */
-    setSessionIdForTest: function(sessionId)
+    sessionId: function()
     {
-        this._sessionId = sessionId;
+        return this._sessionId;
     },
 
     /**
-     * @return {?string}
+     * @param {string} sessionId
+     * @param {!Array.<!WebInspector.TracingModel.EventPayload>} events
      */
-    sessionId: function()
+    setEventsForTest: function(sessionId, events)
     {
-        return this._sessionId;
+        this.reset();
+        this._sessionId = sessionId;
+        this._eventsCollected(events);
+        this._tracingComplete();
     },
 
     /**