Purge AudioOutputDispatcher after close delay if no proxies exist.

media/audio/audio_output_dispatcher_impl.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.
 
 // AudioOutputDispatcherImpl is an implementation of AudioOutputDispatcher.
 //
 // To avoid opening and closing audio devices more frequently than necessary,
 // each dispatcher has a pool of inactive physical streams. A stream is closed
 // only if it hasn't been used for a certain period of time (specified via the
 // constructor).
@@ skipping 42 matching lines @@
 
   void StreamVolumeSet(AudioOutputProxy* stream_proxy, double volume) override;
 
   // Closes |idle_streams_| until the number of |idle_streams_| is equal to the
   // |idle_proxies_| count.  If there are no |idle_proxies_| a single stream is
   // kept alive until |close_timer_| fires.
   void CloseStream(AudioOutputProxy* stream_proxy) override;
 
   void Shutdown() override;
 
+  // Returns true if there are any open AudioOutputProxy objects.
+  bool HasOutputProxies() const;
+
  private:
   friend class base::RefCountedThreadSafe<AudioOutputDispatcherImpl>;
   ~AudioOutputDispatcherImpl() override;
 
   // Creates a new physical output stream, opens it and pushes to
   // |idle_streams_|.  Returns false if the stream couldn't be created or
   // opened.
   bool CreateAndOpenStream();
 
   // Closes all |idle_streams_|.
@@ skipping 16 matching lines @@
   typedef std::map<AudioOutputStream*, int> AudioStreamIDMap;
   AudioStreamIDMap audio_stream_ids_;
   int audio_stream_id_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioOutputDispatcherImpl);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_OUTPUT_DISPATCHER_IMPL_H_