Introduce AudioHardwareConfig for renderer side audio device info.

media/base/audio_hardware_config.h

+// Copyright (c) 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.
+
+#ifndef MEDIA_BASE_AUDIO_HARDWARE_CONFIG_H_
+#define MEDIA_BASE_AUDIO_HARDWARE_CONFIG_H_
+
+#include "base/compiler_specific.h"
+#include "base/synchronization/lock.h"
+#include "media/base/channel_layout.h"
+#include "media/base/media_export.h"
+
+namespace media {
+
+// Provides thread safe access to the audio hardware configuration.
+class MEDIA_EXPORT AudioHardwareConfig {
+ public:
+  AudioHardwareConfig(int output_buffer_size, int output_sample_rate,
+                      int input_sample_rate,
+                      ChannelLayout input_channel_layout);
+  virtual ~AudioHardwareConfig();
+
+  // Accessors for the currently cached hardware configuration.  Safe to call
+  // from any thread.
+  int GetOutputBufferSize();
+  int GetOutputSampleRate();
+  int GetInputSampleRate();
+  ChannelLayout GetInputChannelLayout();
+
+  // Allows callers to update the cached values for either input or output.  The
+  // values are paired under the assumption that these values will only be set
+  // after an input or output device change respectively.  Safe to call from
+  // any thread.
+  void UpdateInputConfig(int sample_rate, media::ChannelLayout channel_layout);
+  void UpdateOutputConfig(int buffer_size, int sample_rate);
+
+ private:
+  // Cached values; access is protected by |config_lock_|.
+  base::Lock config_lock_;
+  int output_buffer_size_;
+  int output_sample_rate_;
+  int input_sample_rate_;
+  ChannelLayout input_channel_layout_;
+
+  DISALLOW_COPY_AND_ASSIGN(AudioHardwareConfig);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_AUDIO_HARDWARE_CONFIG_H_