Implement video frame acknowledgements in the chromoting protocol.

remoting/protocol/message_decoder.h

Index: remoting/protocol/message_decoder.h
diff --git a/remoting/protocol/message_decoder.h b/remoting/protocol/message_decoder.h
index fc42871ddee5dacc6bc5477509f35b002fc324d5..2bcf9d285363524c027f96ad433208449b932ac2 100644
--- a/remoting/protocol/message_decoder.h
+++ b/remoting/protocol/message_decoder.h
@@ -35,6 +35,10 @@ class MessageDecoder {
   MessageDecoder();
   virtual ~MessageDecoder();
 
+  // True if the buffer is empty. If the buffer is empty and GetNextMessage()
+  // returns nullptr it means that the buffer contains incomplete messages.
+  bool is_buffer_empty() { return buffer_.total_bytes() == 0; }
+
   // Add next chunk of data. MessageDecoder retains |data| until all
   // its bytes are consumed.
   void AddData(scoped_refptr<net::IOBuffer> data, int data_size);