Do not pass the string device_id via IPC message to create an audio input stream

content/browser/renderer_host/media/audio_input_device_manager.h

 // Copyright (c) 2012 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.
 //
 // AudioInputDeviceManager manages the audio input devices. In particular it
 // communicates with MediaStreamManager and AudioInputRendererHost on the
-// browser IO thread, handles queries like enumerate/open/close from
-// MediaStreamManager and start/stop from AudioInputRendererHost.
+// browser IO thread, handles queries like
+// enumerate/open/close/GetOpenedDeviceInfoById from MediaStreamManager and
+// GetOpenedDeviceInfoById from AudioInputRendererHost.
 // The work for enumerate/open/close is handled asynchronously on Media Stream
-// device thread, while start/stop are synchronous on the IO thread.
+// device thread, while GetOpenedDeviceInfoById is synchronous on the IO thread.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_INPUT_DEVICE_MANAGER_H_
 #define CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_INPUT_DEVICE_MANAGER_H_
 
 #include <map>
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
 #include "base/threading/thread.h"
 #include "content/browser/renderer_host/media/media_stream_provider.h"
 #include "content/common/content_export.h"
 #include "content/common/media/media_stream_options.h"
 #include "content/public/common/media_stream_request.h"
 
 namespace media {
 class AudioManager;
 }
 
 namespace content {
 
-class AudioInputDeviceManagerEventHandler;
-
 class CONTENT_EXPORT AudioInputDeviceManager : public MediaStreamProvider {
  public:
   // Calling Start() with this kFakeOpenSessionId will open the default device,
   // even though Open() has not been called. This is used to be able to use the
   // AudioInputDeviceManager before MediaStream is implemented.
   static const int kFakeOpenSessionId;
 
   explicit AudioInputDeviceManager(media::AudioManager* audio_manager);
 
+  // Gets the opened device info by |session_id|. If the device is not
+  // opened, it will return an empty object, called on IO thread.
+  StreamDeviceInfo GetOpenedDeviceInfoById(int session_id);

[miu, 2013/03/18 23:19:05]

nit: Consider returning a bool and having the caller provide a pointer to a
StreamDeviceInfo (output argument).  Seems less error-prone than looking at
StreamDeviceInfo and trying to guess whether its uninitialized.

[no longer working on chromium, 2013/03/19 14:06:49]

Then I think it might be clearer to return a const StreamDeviceInfo* for this
GetOpenedDeviceInfoById().
Let me know if you disagree, I can upload a new CL to change it to accept a
pointer for the output.

+
   // MediaStreamProvider implementation, called on IO thread.
   virtual void Register(MediaStreamProviderListener* listener,
                         base::MessageLoopProxy* device_thread_loop) OVERRIDE;
   virtual void Unregister() OVERRIDE;
   virtual void EnumerateDevices(MediaStreamType stream_type) OVERRIDE;
   virtual int Open(const StreamDeviceInfo& device) OVERRIDE;
   virtual void Close(int session_id) OVERRIDE;
 
-  // Functions used by AudioInputRenderHost, called on IO thread.
-  // Starts the device referenced by the session id.
-  void Start(int session_id, AudioInputDeviceManagerEventHandler* handler);
-  // Stops the device referenced by the session id.
-  void Stop(int session_id);
-
   void UseFakeDevice();
   bool ShouldUseFakeDevice() const;
 
  private:
-  typedef std::map<int, AudioInputDeviceManagerEventHandler*> EventHandlerMap;
-  typedef std::map<int, StreamDeviceInfo> StreamDeviceMap;
+  typedef std::vector<StreamDeviceInfo> StreamDeviceList;
   virtual ~AudioInputDeviceManager();
 
   // Enumerates audio input devices on media stream device thread.
   void EnumerateOnDeviceThread(MediaStreamType stream_type);
   // Opens the device on media stream device thread.
-  void OpenOnDeviceThread(int session_id, const StreamDeviceInfo& device);
-  // Closes the deivce on the media stream device thread.
-  void CloseOnDeviceThread(int session_id);
+  void OpenOnDeviceThread(int session_id, const StreamDeviceInfo& info);
 
   // Callback used by EnumerateOnDeviceThread(), called with a list of
   // enumerated devices on IO thread.
   void DevicesEnumeratedOnIOThread(MediaStreamType stream_type,
                                    scoped_ptr<StreamDeviceInfoArray> devices);
   // Callback used by OpenOnDeviceThread(), called with the session_id
   // referencing the opened device on IO thread.
-  void OpenedOnIOThread(MediaStreamType type, int session_id);
+  void OpenedOnIOThread(int session_id, const StreamDeviceInfo& info);
   // Callback used by CloseOnDeviceThread(), called with the session_id
   // referencing the closed device on IO thread.
   void ClosedOnIOThread(MediaStreamType type, int session_id);
 
   // Verifies that the calling thread is media stream device thread.
   bool IsOnDeviceThread() const;
 
+  // Helper to return iterator to the device referenced by |session_id|. If no
+  // device is found, it will return devices_.end().
+  StreamDeviceList::iterator GetDevice(int session_id);

[miu, 2013/03/18 23:19:05]

Suggest you return a StreamDeviceInfo* instead of an iterator here.  Return NULL
to mean not found, etc.

[no longer working on chromium, 2013/03/19 14:06:49]

This iterator returned by GetDevice() is used by Close() to delete the item in
the vector. Returning a StreamDeviceInfo*
 means we need to loop through the vector again to find out what to delete. Hope
it is fine to keep this way.

+
   // Only accessed on Browser::IO thread.
   MediaStreamProviderListener* listener_;
   int next_capture_session_id_;
-  EventHandlerMap event_handlers_;
   bool use_fake_device_;
+  StreamDeviceList devices_;
 
-  // Only accessed from media stream device thread.
-  StreamDeviceMap devices_;
-  media::AudioManager* const audio_manager_;
+  media::AudioManager* const audio_manager_;  // Weak.
 
   // The message loop of media stream device thread that this object runs on.
   scoped_refptr<base::MessageLoopProxy> device_loop_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioInputDeviceManager);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_INPUT_DEVICE_MANAGER_H_