Support for onbufferedamountlow

talk/app/webrtc/objc/RTCDataChannel.mm

 /*
  * libjingle
  * Copyright 2014 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  *  1. Redistributions of source code must retain the above copyright notice,
  *     this list of conditions and the following disclaimer.
  *  2. Redistributions in binary form must reproduce the above copyright notice,
@@ skipping 25 matching lines @@
 namespace webrtc {
 
 class RTCDataChannelObserver : public DataChannelObserver {
  public:
   RTCDataChannelObserver(RTCDataChannel* channel) { _channel = channel; }
 
   void OnStateChange() override {
     [_channel.delegate channelDidChangeState:_channel];
   }
 
+  void OnBufferedAmountChange(uint64 previousAmount) override {

[tkchin_webrtc, 2015/06/30 00:24:11]

nit:
this might look cleaner with a local var (and it'd be more correct too - when
accessing weak ptr twice in a row the second time may return nil while the first
doesn't).
RTCDataChannel* channel = _channel;  (converts to strong ptr)
id<RTCDataChannelDelegate> delegate = channel.delegate;
if ([delegate respondsTo....]) {
etc.
}

+    if ([_channel.delegate
+            respondsToSelector:@selector(channelDidChangeBufferedAmount:
+                                                         previousAmount:)]) {
+      [_channel.delegate channelDidChangeBufferedAmount:_channel
+                                         previousAmount:previousAmount];
+    }
+  }
+
   void OnMessage(const DataBuffer& buffer) override {
     if (!_channel.delegate) {
       return;
     }
     RTCDataBuffer* dataBuffer =
         [[RTCDataBuffer alloc] initWithDataBuffer:buffer];
     [_channel.delegate channel:_channel didReceiveMessageWithBuffer:dataBuffer];
   }
 
  private:
@@ skipping 216 matching lines @@
     _observer.reset(new webrtc::RTCDataChannelObserver(self));
   }
   return self;
 }
 
 - (rtc::scoped_refptr<webrtc::DataChannelInterface>)dataChannel {
   return _dataChannel;
 }
 
 @end