Add AudioStreamRegistry. Move stream counting logic

content/test/mock_audio_stream_registry.h

+// 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.
+
+#ifndef CONTENT_TEST_MOCK_AUDIO_STREAM_REGISTRY_H_
+#define CONTENT_TEST_MOCK_AUDIO_STREAM_REGISTRY_H_
+
+#include "content/browser/renderer_host/media/audio_stream_registry.h"
+#include "content/browser/renderer_host/media/audio_stream_registry_impl.h"
+#include "testing/gmock/include/gmock/gmock.h"
+
+namespace content {
+
+class MockAudioStreamRegistry : public AudioStreamRegistry {
+ public:
+  explicit MockAudioStreamRegistry(int render_process_id);
+  ~MockAudioStreamRegistry() override;
+
+  MOCK_METHOD1(RegisterOutputStream, void(Stream* stream));
+  MOCK_METHOD1(DeregisterOutputStream, void(Stream* stream));
+  MOCK_METHOD2(OutputStreamStateChanged, void(Stream* stream, bool playing));
+
+ private:
+  AudioStreamRegistryImpl impl_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_TEST_MOCK_AUDIO_STREAM_REGISTRY_H_