Support for onbufferedamountlow

talk/app/webrtc/objc/RTCDataChannel.mm

Index: talk/app/webrtc/objc/RTCDataChannel.mm
diff --git a/talk/app/webrtc/objc/RTCDataChannel.mm b/talk/app/webrtc/objc/RTCDataChannel.mm
index 4fb03c284ebbb7e2e1ca8427bfabfee882cfc54f..8a9b6b6095af8dc8bcd6aa09ec4798a6c87c5898 100644
--- a/talk/app/webrtc/objc/RTCDataChannel.mm
+++ b/talk/app/webrtc/objc/RTCDataChannel.mm
@@ -43,6 +43,15 @@ class RTCDataChannelObserver : public DataChannelObserver {
     [_channel.delegate channelDidChangeState:_channel];
   }
 
+  void OnBufferedAmountChange(uint64 previousAmount) override {
+    RTCDataChannel* channel = _channel;
+    id<RTCDataChannelDelegate> delegate = channel.delegate;
+    if ([delegate
+            respondsToSelector:@selector(channel:didChangeBufferedAmount:)]) {
+      [delegate channel:channel didChangeBufferedAmount:previousAmount];
+    }
+  }
+
   void OnMessage(const DataBuffer& buffer) override {
     if (!_channel.delegate) {
       return;