[chromecast] Uses mock backend for MediaPipelineImplTest.

chromecast/media/cma/test/mock_media_pipeline_backend.cc

Index: chromecast/media/cma/test/mock_media_pipeline_backend.cc
diff --git a/chromecast/media/cma/test/mock_media_pipeline_backend.cc b/chromecast/media/cma/test/mock_media_pipeline_backend.cc
new file mode 100644
index 0000000000000000000000000000000000000000..dcaf607d5ab008837b66022a54891a9e7ed7e2c8
--- /dev/null
+++ b/chromecast/media/cma/test/mock_media_pipeline_backend.cc
@@ -0,0 +1,20 @@
+// Copyright 2016 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/cma/test/mock_media_pipeline_backend.h"
+
+namespace chromecast {
+namespace media {
+
+MockAudioDecoder::MockAudioDecoder() {}
+MockAudioDecoder::~MockAudioDecoder() {}
+
+MockVideoDecoder::MockVideoDecoder() {}
+MockVideoDecoder::~MockVideoDecoder() {}
+
+MockMediaPipelineBackend::MockMediaPipelineBackend() {}
+MockMediaPipelineBackend::~MockMediaPipelineBackend() {}
+
+}  // namespace media
+}  // namespace chromecast