Adding some features to proxy.h, and restructuring the macros.

webrtc/api/videosourceproxy.h

Index: webrtc/api/videosourceproxy.h
diff --git a/webrtc/api/videosourceproxy.h b/webrtc/api/videosourceproxy.h
index eaec17bbb1c3688219da5b438c50eb519d3600e0..b678acb0707929c1fd14a55f9a56dfff99569a05 100644
--- a/webrtc/api/videosourceproxy.h
+++ b/webrtc/api/videosourceproxy.h
@@ -21,6 +21,7 @@ namespace webrtc {
 // destroyed on the signaling thread and marshals all method calls to the
 // signaling thread.
 BEGIN_PROXY_MAP(VideoTrackSource)
+  PROXY_SIGNALING_THREAD_DESTRUCTOR()
   PROXY_CONSTMETHOD0(SourceState, state)
   PROXY_CONSTMETHOD0(bool, remote)
   PROXY_CONSTMETHOD0(bool, is_screencast)
@@ -33,7 +34,7 @@ BEGIN_PROXY_MAP(VideoTrackSource)
   PROXY_WORKER_METHOD1(void, RemoveSink, rtc::VideoSinkInterface<VideoFrame>*)
   PROXY_METHOD1(void, RegisterObserver, ObserverInterface*)
   PROXY_METHOD1(void, UnregisterObserver, ObserverInterface*)
-END_PROXY()
+END_PROXY_MAP()
 
 }  // namespace webrtc