Handle audio device changes on Windows.

media/audio/win/audio_manager_win.h

Index: media/audio/win/audio_manager_win.h
diff --git a/media/audio/win/audio_manager_win.h b/media/audio/win/audio_manager_win.h
index 6a4efcbafbd91b11c3773b3fe3786570904e3f81..9c1a27350c10a153c9e10bc0a6d519656a801984 100644
--- a/media/audio/win/audio_manager_win.h
+++ b/media/audio/win/audio_manager_win.h
@@ -12,16 +12,20 @@
 #include "base/compiler_specific.h"
 #include "base/gtest_prod_util.h"
 #include "media/audio/audio_manager_base.h"
+#include "media/audio/win/audio_device_listener_win.h"
 
 namespace media {
 
 // Windows implementation of the AudioManager singleton. This class is internal
 // to the audio output and only internal users can call methods not exposed by
 // the AudioManager class.
-class MEDIA_EXPORT AudioManagerWin : public AudioManagerBase {
+class MEDIA_EXPORT AudioManagerWin
+    : public AudioManagerBase,
+      NON_EXPORTED_BASE(public AudioManager::AudioDeviceListener) {

[scherkus (not reviewing), 2012/10/22 23:51:05]

considering this is win-specific code talking to win-specific code, you can
ditch this implementation, the scary Init() override, and pass a AMWin* pointer
to ADLWin and have it call a non-virtual function

[DaleCurtis, 2012/10/23 01:49:42]

We'll still need the Init() override since we can't call any of the audio device
listener functions until the COM thread has been initialized via audio_thread_.

[scherkus (not reviewing), 2012/10/23 02:23:11]

Huh? ADLWin doesn't run on audio_thread_ and AFAIK COM initialization on one
thread doesn't (shouldn't?) carry over to other threads.

I suspect ADLWin is piggy backing on the COM initialization of whatever thread
called AudioManager::Init()

i.e., main browser thread as content::BrowserMainLoop::MainMessageLoopStart()
calls AudioManager::Create(), which calls AudioManager::Init().

[DaleCurtis, 2012/10/23 03:28:20]

Doh, you're right. How about collapsing the existing Init() into the constructor
and adding an AudioManagerBase::InitializeOnAudioThread() method which can be
overridden/implemented by platform specific audio managers. The constructor will
then post a task upon thread setup completion.

[henrika (OOO until Aug 14), 2012/10/23 07:38:06]

Sounds fine by me. It works today, hence COM init is OK but it would be easier
to follow if we did the new COM parts on the AM thread which we know is COM MTA.

[scherkus (not reviewing), 2012/10/23 17:48:18]

SG.

[DaleCurtis, 2012/10/23 20:09:07]

Split off here: https://codereview.chromium.org/11226057/

[DaleCurtis, 2012/10/23 20:19:43]

Haha, that is totally the wrong link, I meant:
https://codereview.chromium.org/11175066/

  public:
   AudioManagerWin();
   // Implementation of AudioManager.
+  virtual void Init() OVERRIDE;
   virtual bool HasAudioOutputDevices() OVERRIDE;
   virtual bool HasAudioInputDevices() OVERRIDE;
   virtual string16 GetAudioInputDeviceModel() OVERRIDE;
@@ -42,6 +46,9 @@ class MEDIA_EXPORT AudioManagerWin : public AudioManagerBase {
   virtual AudioParameters GetPreferredLowLatencyOutputStreamParameters(
       const AudioParameters& input_params) OVERRIDE;
 
+  // AudioDeviceListener implementation.
+  virtual void OnDeviceChange() OVERRIDE;
+
  protected:
   virtual ~AudioManagerWin();
 
@@ -70,6 +77,9 @@ class MEDIA_EXPORT AudioManagerWin : public AudioManagerBase {
       const AudioParameters& params,
       const std::string& device_id);
 
+  // Listen for output device changes.
+  scoped_ptr<AudioDeviceListenerWin> output_device_listener_;
+
   DISALLOW_COPY_AND_ASSIGN(AudioManagerWin);
 };