Revert of Adding "first packet received" notification to PeerConnectionObserver.

talk/app/webrtc/objctests/RTCPeerConnectionSyncObserver.m

 /*
  * libjingle
  * Copyright 2013 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 215 matching lines @@
   NSString* expectedLabel =
       [self popFirstElementAsNSString:_expectedDataChannels];
   NSAssert([expectedLabel isEqual:dataChannel.label],
            @"Data channel not expected");
   self.dataChannel = dataChannel;
   dataChannel.delegate = self;
   NSAssert(kRTCDataChannelStateConnecting == dataChannel.state,
            @"Unexpected state");
 }
 
-- (void)peerConnectionOnFirstMediaPacketReceived:
-    (RTCPeerConnection*)peerConnection {
-}
-
 #pragma mark - RTCDataChannelDelegate
 
 - (void)channelDidChangeState:(RTCDataChannel*)channel {
   NSAssert([_expectedStateChanges count] > 0,
            @"Unexpected state change");
   int expectedState = [self popFirstElementAsInt:_expectedStateChanges];
   NSAssert(expectedState == channel.state, @"Channel state should match");
 }
 
 - (void)channel:(RTCDataChannel*)channel
     didChangeBufferedAmount:(NSUInteger)previousAmount {
   NSAssert(channel.bufferedAmount != previousAmount,
            @"Invalid bufferedAmount change");
 }
 
 - (void)channel:(RTCDataChannel*)channel
     didReceiveMessageWithBuffer:(RTCDataBuffer*)buffer {
   NSAssert([_expectedMessages count] > 0,
            @"Unexpected message received");
   RTCDataBuffer* expectedBuffer = [_expectedMessages objectAtIndex:0];
   NSAssert(expectedBuffer.isBinary == buffer.isBinary,
            @"Buffer isBinary should match");
   NSAssert([expectedBuffer.data isEqual:buffer.data],
            @"Buffer data should match");
   [_expectedMessages removeObjectAtIndex:0];
 }
 
 @end