Makes AudioOutputProxy -> AudioOutputDispatcher reference weak.

media/audio/audio_output_dispatcher.h

Index: media/audio/audio_output_dispatcher.h
diff --git a/media/audio/audio_output_dispatcher.h b/media/audio/audio_output_dispatcher.h
index f94f95f65389c657cef60a3393acc0ceebbd45f0..92aaf3d5e196b388cbca43b863be2569e89d5a1a 100644
--- a/media/audio/audio_output_dispatcher.h
+++ b/media/audio/audio_output_dispatcher.h
@@ -19,6 +19,7 @@
 #define MEDIA_AUDIO_AUDIO_OUTPUT_DISPATCHER_H_
 
 #include "base/macros.h"
+#include "base/memory/weak_ptr.h"
 #include "media/audio/audio_io.h"
 #include "media/audio/audio_manager.h"
 #include "media/base/audio_parameters.h"
@@ -31,7 +32,8 @@ namespace media {
 
 class AudioOutputProxy;
 
-class MEDIA_EXPORT AudioOutputDispatcher {
+class MEDIA_EXPORT AudioOutputDispatcher
+    : public base::SupportsWeakPtr<AudioOutputDispatcher> {

[DaleCurtis, 2017/01/10 20:54:40]

Instead of adding this can you make the constructor private and add a Create()
method which returns a WeakPtr? SupportsWeakPtr is a bit too permissive.

[alokp, 2017/01/10 22:51:26]

A Create method will not work because AMB still needs to hold a
unique_ptr<AudioOutputDispatcher>. We just need the WeakPtr for AOPs. I could
add a virtual AudioOutputDispatcher::GetWeakPtr, but I am not sure if it would
be any better than deriving from SupportsWeakPtr.

[DaleCurtis, 2017/01/10 22:58:08]

what about AOD::CreateProxy() which returns an AudioOutputProxy using the
internal WeakPtr?

[alokp, 2017/01/10 23:31:53]

Yes - this should work. Done.

  public:
   AudioOutputDispatcher(AudioManager* audio_manager,
                         const AudioParameters& params,