[chromecast] Moves CastAudioOutputStream::Backend to CMA thread.

chromecast/media/BUILD.gn

 # Copyright 2015 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.
 
 import("//chromecast/chromecast.gni")
 import("//testing/test.gni")
 
 group("media") {
   public_deps = [
     "//chromecast/media/audio",
     "//chromecast/media/base",
     "//chromecast/media/cdm",
     "//chromecast/media/cma",
   ]
 }
 
 test("cast_media_unittests") {
   sources = [
+    "audio/cast_audio_manager_unittest.cc",
     "audio/cast_audio_mixer_unittest.cc",
     "audio/cast_audio_output_stream_unittest.cc",
     "base/media_resource_tracker_unittest.cc",
     "base/supported_codec_profile_levels_memo_unittest.cc",
     "test/run_all_unittests.cc",
   ]
 
   deps = [
     ":media",
     "//base",
     "//base/test:test_support",
     "//chromecast/base",
     "//chromecast/base/metrics:test_support",
+    "//chromecast/media/cma:test_support",
     "//chromecast/public",
     "//media",
     "//media/audio:test_support",
     "//media/base:test_support",
     "//testing/gmock",
     "//testing/gtest",
   ]
 
   if (!is_android) {
     deps += [ "//chromecast/media/cma:unittests" ]
   }
 }