Reland of Fixed the audio backgrounding bug

content/browser/renderer_host/render_process_host_impl.h

Index: content/browser/renderer_host/render_process_host_impl.h
diff --git a/content/browser/renderer_host/render_process_host_impl.h b/content/browser/renderer_host/render_process_host_impl.h
index a648d2db63cb540bf3adb919138de5113497745c..d05bd3ed2676e51ab09aac5e54dcc762d0b556c6 100644
--- a/content/browser/renderer_host/render_process_host_impl.h
+++ b/content/browser/renderer_host/render_process_host_impl.h
@@ -113,6 +113,7 @@
   void WidgetRestored() override;
   void WidgetHidden() override;
   int VisibleWidgetCount() const override;
+  void AudioStateChanged() override;
   bool IsForGuestsOnly() const override;
   StoragePartition* GetStoragePartition() const override;
   bool Shutdown(int exit_code, bool wait) override;
@@ -317,8 +318,10 @@
       const base::CommandLine& browser_cmd,
       base::CommandLine* renderer_cmd) const;
 
-  // Callers can reduce the RenderProcess' priority.
-  void SetBackgrounded(bool backgrounded);
+  // Inspects the current object state and sets/removes background priority if
+  // appropriate. Should be called after any of the involved data members
+  // change.
+  void UpdateProcessPriority();
 
   // Handle termination of our process.
   void ProcessDied(bool already_dead, RendererClosedDetails* known_details);
@@ -350,8 +353,9 @@
   // backgrounded.
   int32 visible_widgets_;
 
-  // Does this process have backgrounded priority.
-  bool backgrounded_;
+  // Whether this process currently has backgrounded priority. Tracked so that
+  // UpdateProcessPriority() can avoid redundantly setting the priority.
+  bool is_process_backgrounded_;
 
   // Used to allow a RenderWidgetHost to intercept various messages on the
   // IO thread.