[Cast] Remove AudioDecoder's dependency on WebRTC, and refactor/clean-up AudioReceiver.

media/cast/audio_receiver/audio_receiver.gypi

 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'targets': [
     {
       'target_name': 'cast_audio_receiver',
       'type': 'static_library',
       'include_dirs': [
         '<(DEPTH)/',
         '<(DEPTH)/third_party/',
         '<(DEPTH)/third_party/webrtc/',
       ],
       'sources': [
         'audio_decoder.h',
         'audio_decoder.cc',
         'audio_receiver.h',
         'audio_receiver.cc',
       ], # source
       'dependencies': [
+        '<(DEPTH)/media/media.gyp:media',
+        '<(DEPTH)/media/media.gyp:shared_memory_support',
         '<(DEPTH)/media/cast/transport/utility/utility.gyp:transport_utility',
         '<(DEPTH)/media/cast/rtcp/rtcp.gyp:cast_rtcp',
         '<(DEPTH)/media/cast/rtp_receiver/rtp_receiver.gyp:cast_rtp_receiver',
-        '<(DEPTH)/third_party/webrtc/webrtc.gyp:webrtc',
+        '<(DEPTH)/third_party/opus/opus.gyp:opus',
       ],
     },
   ],
 }