[Cast] Remove AudioDecoder's dependency on WebRTC, and refactor/clean-up AudioReceiver.

media/cast/video_receiver/video_receiver.cc

Index: media/cast/video_receiver/video_receiver.cc
diff --git a/media/cast/video_receiver/video_receiver.cc b/media/cast/video_receiver/video_receiver.cc
index f2331e14a40facb5f93503a64d305cc5bf602cb0..310866d83b96882931674630f19c00495fc14f02 100644
--- a/media/cast/video_receiver/video_receiver.cc
+++ b/media/cast/video_receiver/video_receiver.cc
@@ -39,9 +39,9 @@ class LocalRtpVideoData : public RtpData {
 
   virtual void OnReceivedPayloadData(const uint8* payload_data,
                                      size_t payload_size,
-                                     const RtpCastHeader* rtp_header) OVERRIDE {
+                                     const RtpCastHeader& rtp_header) OVERRIDE {
     video_receiver_->IncomingParsedRtpPacket(
-        payload_data, payload_size, *rtp_header);
+        payload_data, payload_size, rtp_header);
   }
 
  private: