Support counter graphs in Timeline based on trace events

Source/devtools/front_end/timeline/TimelineModelImpl.js

Index: Source/devtools/front_end/timeline/TimelineModelImpl.js
diff --git a/Source/devtools/front_end/timeline/TimelineModelImpl.js b/Source/devtools/front_end/timeline/TimelineModelImpl.js
index 8bbc5aaad0000733d4a5f82ea2de6314250bd7ea..4906f3828f237c8b7e26336a1b0fcf5cba336969 100644
--- a/Source/devtools/front_end/timeline/TimelineModelImpl.js
+++ b/Source/devtools/front_end/timeline/TimelineModelImpl.js
@@ -482,6 +482,14 @@ WebInspector.TimelineModel.RecordImpl.prototype = {
     /**
      * @return {?Object}
      */
+    counters: function()
+    {
+        return this.type() === WebInspector.TimelineModel.RecordType.UpdateCounters ? this.data() : null;
+    },
+
+    /**
+     * @return {?Object}
+     */
     highlightQuad: function()
     {
         var quad = null;