Revert of [chromecast] Pass media task runner to MediaPipelineBackendManager.

chromecast/media/audio/cast_audio_output_stream_unittest.cc

 // 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.
 
 #include "chromecast/media/audio/cast_audio_output_stream.h"
 
 #include <stddef.h>
 #include <stdint.h>
 #include <utility>
 
@@ skipping 167 matching lines @@
   }
   void OnError(::media::AudioOutputStream* stream) override { error_ = true; }
 
  private:
   bool error_;
 };
 
 class FakeAudioManager : public CastAudioManager {
  public:
   FakeAudioManager()
-      : CastAudioManager(nullptr, nullptr), media_pipeline_backend_(nullptr) {}
+      : CastAudioManager(nullptr), media_pipeline_backend_(nullptr) {}
   ~FakeAudioManager() override {}
 
   // CastAudioManager overrides.
   scoped_ptr<MediaPipelineBackend> CreateMediaPipelineBackend(
       const MediaPipelineDeviceParams& params) override {
     DCHECK(media::MediaMessageLoop::GetTaskRunner()->BelongsToCurrentThread());
     DCHECK(!media_pipeline_backend_);
 
     scoped_ptr<FakeMediaPipelineBackend> backend(
         new FakeMediaPipelineBackend());
@@ skipping 448 matching lines @@
 TEST_F(CastAudioOutputStreamTest, CloseWithoutStart) {
   ::media::AudioOutputStream* stream = CreateStream();
   ASSERT_TRUE(stream);
   ASSERT_TRUE(OpenStream(stream));
   CloseStream(stream);
 }
 
 }  // namespace
 }  // namespace media
 }  // namespace chromecast