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

chrome/browser/ui/tabs/tab_strip_model_observer.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 CHROME_BROWSER_UI_TABS_TAB_STRIP_MODEL_OBSERVER_H_
 #define CHROME_BROWSER_UI_TABS_TAB_STRIP_MODEL_OBSERVER_H_
 
+#include <string>
+
 class TabStripModel;
 
 namespace content {
 class WebContents;
 }
 
 namespace ui {
 class ListSelectionModel;
 }
 
@@ skipping 104 matching lines @@
   // prerendering swaps in a prerendered WebContents.
   virtual void TabReplacedAt(TabStripModel* tab_strip_model,
                              content::WebContents* old_contents,
                              content::WebContents* new_contents,
                              int index);
 
   // Invoked when the pinned state of a tab changes. See note in
   // TabMiniStateChanged as to how this relates to TabMiniStateChanged.
   virtual void TabPinnedStateChanged(content::WebContents* contents, int index);
 
+  // Invoked when the audible or muted states change.
+  virtual void TabAudibleStateChanged(content::WebContents* contents,

[sky, 2015/02/02 15:43:06]

I don't think this makes sense in the TabStripModel. Why put it here?

+                                      bool audible);
+  virtual void TabMutedStateChanged(content::WebContents* contents,
+                                    bool muted,
+                                    const std::string& cause);
+
   // Invoked if the mini state of a tab changes.
   // NOTE: This is sent when the pinned state of a non-app tab changes and is
   // sent in addition to TabPinnedStateChanged. UI code typically need not care
   // about TabPinnedStateChanged, but instead this.
   virtual void TabMiniStateChanged(content::WebContents* contents, int index);
 
   // Invoked when the blocked state of a tab changes.
   // NOTE: This is invoked when a tab becomes blocked/unblocked by a tab modal
   // window.
   virtual void TabBlockedStateChanged(content::WebContents* contents,
@@ skipping 15 matching lines @@
 
   // Sent when the tabstrip model is about to be deleted and any reference held
   // must be dropped.
   virtual void TabStripModelDeleted();
 
  protected:
   virtual ~TabStripModelObserver() {}
 };
 
 #endif  // CHROME_BROWSER_UI_TABS_TAB_STRIP_MODEL_OBSERVER_H_