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

chrome/app/generated_resources.grd

Index: chrome/app/generated_resources.grd
diff --git a/chrome/app/generated_resources.grd b/chrome/app/generated_resources.grd
index e1c2888a9e6c06d98019f2204b23b6b8d91ca7e7..b3b64c478835eee7654103218fbc030cce55156b 100644
--- a/chrome/app/generated_resources.grd
+++ b/chrome/app/generated_resources.grd
@@ -8468,6 +8468,18 @@ Keep your key file in a safe place. You will need it to create new versions of y
         <message name="IDS_TAB_CXMENU_UNPIN_TABS" desc="The label of the tab context menu item for unpinning multiple tab.">
           Unpin tabs
         </message>
+        <message name="IDS_TAB_CXMENU_AUDIO_MUTE_TAB" desc="The label of the tab context menu item for muting a single tab.">
+          Mute tab
+        </message>
+        <message name="IDS_TAB_CXMENU_AUDIO_MUTE_TABS" desc="The label of the tab context menu item for muting more than one tab.">
+          Mute tabs
+        </message>
+        <message name="IDS_TAB_CXMENU_AUDIO_UNMUTE_TAB" desc="The label of the tab context menu item for unmuting a single tab.">
+          Unmute tab
+        </message>
+        <message name="IDS_TAB_CXMENU_AUDIO_UNMUTE_TABS" desc="The label of the tab context menu item for unmuting more than one tab.">
+          Unmute tabs
+        </message>
         <message name="IDS_TAB_CXMENU_BOOKMARK_ALL_TABS" desc="The label of the tab context menu item for creating a bookmark folder containing an entry for each open tab.">
           Bookmark all tabs...
         </message>
@@ -14407,6 +14419,9 @@ Do you accept?
     <message name="IDS_TOOLTIP_TAB_MEDIA_STATE_AUDIO_PLAYING" desc="Extra tool tip text, when the tab is playing audio.">
       This tab is playing audio.
     </message>
+    <message name="IDS_TOOLTIP_TAB_MEDIA_STATE_AUDIO_MUTING" desc="Extra tool tip text, when all tab audio output is muted.">
+      This tab's audio is being muted.
+    </message>
 
     <!-- ProcessSingleton -->
     <message name="IDS_PROFILE_IN_USE_LINUX_QUIT" desc="Text of button in profile in use dialog to quit without doing anything.">