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

chrome/chrome_browser_ui.gypi

 # Copyright 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.
 
 {
   'variables': {
     'chrome_browser_ui_non_ios_sources': [
       'browser/ui/accelerator_utils.h',
       'browser/ui/android/android_about_app_info.cc',
       'browser/ui/android/android_about_app_info.h',
@@ skipping 2191 matching lines @@
       'browser/ui/views/sync/profile_signin_confirmation_dialog_views.cc',
       'browser/ui/views/sync/profile_signin_confirmation_dialog_views.h',
       'browser/ui/views/tab_contents/chrome_web_contents_view_delegate_views.cc',
       'browser/ui/views/tab_contents/chrome_web_contents_view_delegate_views.h',
       'browser/ui/views/tab_icon_view.cc',
       'browser/ui/views/tab_icon_view.h',
       'browser/ui/views/tab_modal_confirm_dialog_views.cc',
       'browser/ui/views/tab_modal_confirm_dialog_views.h',
       'browser/ui/views/tabs/browser_tab_strip_controller.cc',
       'browser/ui/views/tabs/browser_tab_strip_controller.h',
+      'browser/ui/views/tabs/media_indicator_button.cc',
+      'browser/ui/views/tabs/media_indicator_button.h',
       'browser/ui/views/tabs/stacked_tab_strip_layout.cc',
       'browser/ui/views/tabs/stacked_tab_strip_layout.h',
       'browser/ui/views/tabs/tab.cc',
       'browser/ui/views/tabs/tab_controller.h',
       'browser/ui/views/tabs/tab_drag_controller.cc',
       'browser/ui/views/tabs/tab_drag_controller.h',
       'browser/ui/views/tabs/tab.h',
       'browser/ui/views/tabs/tab_strip.cc',
       'browser/ui/views/tabs/tab_strip_controller.h',
       'browser/ui/views/tabs/tab_strip.h',
@@ skipping 759 matching lines @@
         }],
         ['OS!="android" and OS!="ios"', {
           'dependencies': [
             '../device/bluetooth/bluetooth.gyp:device_bluetooth',
           ],
         }],
       ],
     },
   ],
 }