Implement HTMLMediaElement::srcObject.

Source/modules/mediastream/MediaStream.h

Index: Source/modules/mediastream/MediaStream.h
diff --git a/Source/modules/mediastream/MediaStream.h b/Source/modules/mediastream/MediaStream.h
index 7e6748ee92c6a746dcdb46e7016560272adcd907..214cd09f88459c8d86a24e8b3b909be02d547c41 100644
--- a/Source/modules/mediastream/MediaStream.h
+++ b/Source/modules/mediastream/MediaStream.h
@@ -27,6 +27,7 @@
 #define MediaStream_h
 
 #include "core/dom/ContextLifecycleObserver.h"
+#include "core/html/MediaProvider.h"
 #include "core/html/URLRegistry.h"
 #include "modules/EventTargetModules.h"
 #include "modules/mediastream/MediaStreamTrack.h"
@@ -40,6 +41,7 @@ class ExceptionState;
 class MediaStream FINAL
     : public RefCountedGarbageCollectedWillBeGarbageCollectedFinalized<MediaStream>
     , public URLRegistrable
+    , public MediaProvider
     , public MediaStreamDescriptorClient
     , public EventTargetWithInlineData
     , public ContextLifecycleObserver {
@@ -88,6 +90,10 @@ public:
     // URLRegistrable
     virtual URLRegistry& registry() const OVERRIDE;
 
+    // MediaProvider
+    virtual EventTarget* eventTarget() OVERRIDE { return this; }
+    virtual const String& getObjectUrl() OVERRIDE;
+
     virtual void trace(Visitor*) OVERRIDE;
 
 private:
@@ -105,6 +111,7 @@ private:
     void scheduledEventTimerFired(Timer<MediaStream>*);
 
     bool m_stopped;
+    String m_objectUrl;
 
     MediaStreamTrackVector m_audioTracks;
     MediaStreamTrackVector m_videoTracks;