Avoid shutdown crash if audio thread is hung.

media/audio/audio_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.
 
 #ifndef MEDIA_AUDIO_AUDIO_MANAGER_H_
 #define MEDIA_AUDIO_AUDIO_MANAGER_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 65 matching lines @@
 
   // Returns the app name or an empty string if it is not set.
   static const std::string& GetGlobalAppName();
 #endif
 
   // Returns the pointer to the last created instance, or NULL if not yet
   // created. This is a utility method for the code outside of media directory,
   // like src/chrome.
   static AudioManager* Get();
 
-  // Releases all audio resources.
+  // Synchronously releases all audio resources.
   // Must be called before deletion and on the same thread as AudioManager
   // was created.
-  void Shutdown();
+  // Returns true on success but false if AudioManager could not be shutdown.
+  // AudioManager instance must not be deleted if shutdown failed.
+  bool Shutdown();
 
   // Log callback used for sending log messages from a stream to the object
   // that manages the stream.
   using LogCallback = base::Callback<void(const std::string&)>;
 
   // Factory for all the supported stream formats. |params| defines parameters
   // of the audio stream to be created.
   //
   // |params.sample_per_packet| is the requested buffer allocation which the
   // audio source thinks it can usually fill without blocking. Internally two
@@ skipping 169 matching lines @@
   std::unique_ptr<AudioThread> audio_thread_;
   bool shutdown_ = false;  // True after |this| has been shutdown.
 
   THREAD_CHECKER(thread_checker_);
   DISALLOW_COPY_AND_ASSIGN(AudioManager);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_MANAGER_H_