Add MediaStreamSource frame rate calculation to the tracker.

content/renderer/media/webrtc/video_destination_handler.cc

Index: content/renderer/media/webrtc/video_destination_handler.cc
diff --git a/content/renderer/media/webrtc/video_destination_handler.cc b/content/renderer/media/webrtc/video_destination_handler.cc
index 54cf603c5ae49c22e2652331d6c60079f8bb7ab4..41d36bb3605648d5ed9364c8774bcdbe498d5628 100644
--- a/content/renderer/media/webrtc/video_destination_handler.cc
+++ b/content/renderer/media/webrtc/video_destination_handler.cc
@@ -24,6 +24,8 @@
 
 namespace content {
 
+const char kTypeName[] = "Pepper Plugin";
+
 class PpFrameWriter::FrameWriterDelegate
     : public base::RefCountedThreadSafe<FrameWriterDelegate> {
  public:
@@ -107,6 +109,10 @@ void PpFrameWriter::StopSourceImpl() {
   DCHECK(CalledOnValidThread());
 }
 
+std::string PpFrameWriter::TypeName() const {
+  return kTypeName;
+}
+
 void PpFrameWriter::PutFrame(PPB_ImageData_Impl* image_data,
                              int64 time_stamp_ns) {
   DCHECK(CalledOnValidThread());