Fixed the audio backgrounding bug

content/browser/renderer_host/render_process_host_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.
 
 #ifndef CONTENT_BROWSER_RENDERER_HOST_RENDER_PROCESS_HOST_IMPL_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_PROCESS_HOST_IMPL_H_
 
 #include <map>
 #include <queue>
 #include <string>
@@ skipping 94 matching lines @@
   bool Init() override;
   int GetNextRoutingID() override;
   void AddRoute(int32 routing_id, IPC::Listener* listener) override;
   void RemoveRoute(int32 routing_id) override;
   void AddObserver(RenderProcessHostObserver* observer) override;
   void RemoveObserver(RenderProcessHostObserver* observer) override;
   void ShutdownForBadMessage() override;
   void WidgetRestored() override;
   void WidgetHidden() override;
   int VisibleWidgetCount() const override;
+  void AudioStopped() override;
+  void AudioStarted() override;
   bool IsForGuestsOnly() const override;
   StoragePartition* GetStoragePartition() const override;
   bool Shutdown(int exit_code, bool wait) override;
   bool FastShutdownIfPossible() override;
   base::ProcessHandle GetHandle() const override;
   BrowserContext* GetBrowserContext() const override;
   bool InSameStoragePartition(StoragePartition* partition) const override;
   int GetID() const override;
   bool HasConnection() const override;
   void SetIgnoreInputEvents(bool ignore_input_events) override;
@@ skipping 198 matching lines @@
   void AppendRendererCommandLine(base::CommandLine* command_line) const;
 
   // Copies applicable command line switches from the given |browser_cmd| line
   // flags to the output |renderer_cmd| line flags. Not all switches will be
   // copied over.
   void PropagateBrowserCommandLineToRenderer(
       const base::CommandLine& browser_cmd,
       base::CommandLine* renderer_cmd) const;
 
   // Callers can reduce the RenderProcess' priority.
+  // Must be called from the IO thread.

[ncarter (slow), 2015/07/06 21:53:57]

I think you mean UI thread (since that's what the DCHECK says).

In any case, RenderProcessHost is single-threaded and only exists on the UI
thread.

[sebsg, 2015/08/02 16:44:23]

Done.

   void SetBackgrounded(bool backgrounded);
 
   // Handle termination of our process.
   void ProcessDied(bool already_dead, RendererClosedDetails* known_details);
 
   // GpuSwitchingObserver implementation.
   void OnGpuSwitched() override;
 
 #if defined(ENABLE_WEBRTC)
   void OnRegisterAecDumpConsumer(int id);
@@ skipping 165 matching lines @@
 #endif
 
   base::WeakPtrFactory<RenderProcessHostImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderProcessHostImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_PROCESS_HOST_IMPL_H_