Added mute logic to VideoTrackRenderers.

talk/app/webrtc/videotrackrenderers.cc

Index: talk/app/webrtc/videotrackrenderers.cc
diff --git a/talk/app/webrtc/videotrackrenderers.cc b/talk/app/webrtc/videotrackrenderers.cc
index 3f9301b7185d88789877c39f985ae150e4e8158f..5b890371a55dd6bacf56cf0ea305eb02bd1a2f1c 100644
--- a/talk/app/webrtc/videotrackrenderers.cc
+++ b/talk/app/webrtc/videotrackrenderers.cc
@@ -26,7 +26,7 @@
  */
 
 #include "talk/app/webrtc/videotrackrenderers.h"
-#include "talk/media/base/videoframe.h"
+#include "talk/media/webrtc/webrtcvideoframe.h"
 
 namespace webrtc {
 
@@ -55,14 +55,44 @@ void VideoTrackRenderers::SetEnabled(bool enable) {
 }
 
 bool VideoTrackRenderers::RenderFrame(const cricket::VideoFrame* frame) {
-  rtc::CritScope cs(&critical_section_);
-  if (!enabled_) {
+  {
+    rtc::CritScope cs(&critical_section_);
+    if (enabled_) {
+      RenderFrameToRenderers(frame);
+      return true;
+    }
+  }
+
+  // Generate the black frame outside of the critical section. Note
+  // that this may result in unexpected frame order, in the unlikely
+  // case that RenderFrame is called from multiple threads without
+  // proper serialization, and the track is switched from disabled to
+  // enabled in the middle of the first call.
+  cricket::WebRtcVideoFrame black(new rtc::RefCountedObject<I420Buffer>(
+                                      static_cast<int>(frame->GetWidth()),
+                                      static_cast<int>(frame->GetHeight())),
+                                  frame->GetTimeStamp(),
+                                  frame->GetVideoRotation());
+  black.SetToBlack();
+
+  {
+    rtc::CritScope cs(&critical_section_);
+    // Check enabled_ flag again, since the track might have been
+    // enabled while we generated the black frame. I think the
+    // enabled-ness ought to be applied at the track output, and hence
+    // an enabled track shouldn't send any blacked out frames.
+    RenderFrameToRenderers(enabled_ ? frame : &black);
+
     return true;
   }
+}
+
+// Called with critical_section_ already locked
+void VideoTrackRenderers::RenderFrameToRenderers(
+    const cricket::VideoFrame* frame) {
   for (VideoRendererInterface* renderer : renderers_) {
     renderer->RenderFrame(frame);
   }
-  return true;
 }
 
 }  // namespace webrtc