Revert of Use CopyOnWriteBuffer instead of Buffer to avoid unnecessary copies.

webrtc/api/webrtcsession.h

Index: webrtc/api/webrtcsession.h
diff --git a/webrtc/api/webrtcsession.h b/webrtc/api/webrtcsession.h
index 07e432661fb93ed99c70cc06bc1d53aa26557c9e..27472c9136ccb1d02fbfa3f10397ccce3d5deb97 100644
--- a/webrtc/api/webrtcsession.h
+++ b/webrtc/api/webrtcsession.h
@@ -255,7 +255,7 @@
 
   // Implements DataChannelProviderInterface.
   bool SendData(const cricket::SendDataParams& params,
-                const rtc::CopyOnWriteBuffer& payload,
+                const rtc::Buffer& payload,
                 cricket::SendDataResult* result) override;
   bool ConnectDataChannel(DataChannel* webrtc_data_channel) override;
   void DisconnectDataChannel(DataChannel* webrtc_data_channel) override;
@@ -397,7 +397,7 @@
   // messages.
   void OnDataChannelMessageReceived(cricket::DataChannel* channel,
                                     const cricket::ReceiveDataParams& params,
-                                    const rtc::CopyOnWriteBuffer& payload);
+                                    const rtc::Buffer& payload);
 
   std::string BadStateErrMsg(State state);
   void SetIceConnectionState(PeerConnectionInterface::IceConnectionState state);