Get rid of media_engine_ from BaseChannel; only VoiceChannel needs it.

talk/session/media/channel_unittest.cc

 /*
  * libjingle
  * Copyright 2009 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 1862 matching lines @@
   }
 };
 
 // override to add NULL parameter
 template<>
 cricket::VideoChannel* ChannelTest<VideoTraits>::CreateChannel(
     rtc::Thread* thread, cricket::MediaEngineInterface* engine,
     cricket::FakeVideoMediaChannel* ch, cricket::BaseSession* session,
     bool rtcp) {
   cricket::VideoChannel* channel = new cricket::VideoChannel(
-      thread, engine, ch, session, cricket::CN_VIDEO, rtcp);
+      thread, ch, session, cricket::CN_VIDEO, rtcp);
   if (!channel->Init()) {
     delete channel;
     channel = NULL;
   }
   return channel;
 }
 
 // override to add 0 parameter
 template<>
 bool ChannelTest<VideoTraits>::AddStream1(int id) {
@@ skipping 980 matching lines @@
   };
   rtc::Buffer payload(data, 3);
   cricket::SendDataResult result;
   ASSERT_TRUE(media_channel1_->SendData(params, payload, &result));
   EXPECT_EQ(params.ssrc,
             media_channel1_->last_sent_data_params().ssrc);
   EXPECT_EQ("foo", media_channel1_->last_sent_data());
 }
 
 // TODO(pthatcher): TestSetReceiver?