Make tab audible and muted states and cause available for an extension API

content/public/browser/web_contents.h

Index: content/public/browser/web_contents.h
diff --git a/content/public/browser/web_contents.h b/content/public/browser/web_contents.h
index 5478a378158c5dd4dcacfb8184555724693550dd..27a90c478129d29409192e72c5936379cab65db9 100644
--- a/content/public/browser/web_contents.h
+++ b/content/public/browser/web_contents.h
@@ -308,7 +308,10 @@ class WebContents : public PageNavigator,
 
   // Indicates/Sets whether all audio output from this WebContents is muted.
   virtual bool IsAudioMuted() const = 0;
-  virtual void SetAudioMuted(bool mute) = 0;
+  virtual void SetAudioMuted(bool muted, const std::string& cause) = 0;
+
+  // Get source (initial, user, capture, extensionid) for the tab's muted state
+  virtual const std::string& GetAudioMutedCause() const = 0;
 
   // Indicates whether this tab should be considered crashed. The setter will
   // also notify the delegate when the flag is changed.