Tab audio mute control (views UI), behind a switch (off by default).

chrome/browser/ui/tabs/tab_strip_model.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_H_
 #define CHROME_BROWSER_UI_TABS_TAB_STRIP_MODEL_H_
 
 #include <vector>
 
 #include "base/memory/scoped_ptr.h"
@@ skipping 394 matching lines @@
   enum ContextMenuCommand {
     CommandFirst = 0,
     CommandNewTab,
     CommandReload,
     CommandDuplicate,
     CommandCloseTab,
     CommandCloseOtherTabs,
     CommandCloseTabsToRight,
     CommandRestoreTab,
     CommandTogglePinned,
+    CommandToggleTabAudioMuted,
     CommandBookmarkAllTabs,
     CommandSelectByDomain,
     CommandSelectByOpener,
     CommandLast
   };
 
   // Returns true if the specified command is enabled. If |context_index| is
   // selected the response applies to all selected tabs.
   bool IsContextMenuCommandEnabled(int context_index,
                                    ContextMenuCommand command_id) const;
@@ skipping 150 matching lines @@
 
   // TODO(sky): remove this; used for debugging 291265.
   bool in_notify_;
 
   base::WeakPtrFactory<TabStripModel> weak_factory_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(TabStripModel);
 };
 
 #endif  // CHROME_BROWSER_UI_TABS_TAB_STRIP_MODEL_H_