Add UseCounter for MediaStreamTrack.getSources.

Source/modules/mediastream/MediaStreamTrack.idl

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in the
@@ skipping 14 matching lines @@
 [
     GarbageCollected,
     ActiveDOMObject
 ] interface MediaStreamTrack : EventTarget {
     readonly attribute DOMString kind;
     readonly attribute DOMString id;
     readonly attribute DOMString label;
     attribute boolean enabled;
     readonly attribute DOMString readyState;
 
-    [CallWith=ExecutionContext, RaisesException] static void getSources(MediaStreamTrackSourcesCallback callback);
+    [CallWith=ExecutionContext, RaisesException, MeasureAs=MediaStreamTrackGetSources] static void getSources(MediaStreamTrackSourcesCallback callback);
     [ImplementedAs=stopTrack, RaisesException] void stop();
     [CallWith=ExecutionContext] MediaStreamTrack clone();
 
     attribute EventHandler onmute;
     attribute EventHandler onunmute;
     attribute EventHandler onended;
 };