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

chrome/browser/ui/tabs/tab_strip_model.h

Index: chrome/browser/ui/tabs/tab_strip_model.h
diff --git a/chrome/browser/ui/tabs/tab_strip_model.h b/chrome/browser/ui/tabs/tab_strip_model.h
index 25279468d2cb3887ab2263fbfecfc22610cb54c1..62cbefcf12c9763231975b45c526d32143cfc03c 100644
--- a/chrome/browser/ui/tabs/tab_strip_model.h
+++ b/chrome/browser/ui/tabs/tab_strip_model.h
@@ -325,6 +325,12 @@ class TabStripModel {
   // See description above class for details on pinned tabs.
   bool IsTabPinned(int index) const;
 
+  // Changes the muted audio state of the tab at |index|.
+  void SetTabAudioMuted(int index, bool mute);
+
+  // Returns true if the tab at |index| is muting its audio.
+  bool IsTabAudioMuted(int index) const;
+
   // Is the tab a mini-tab?
   // See description above class for details on this.
   bool IsMiniTab(int index) const;
@@ -412,6 +418,7 @@ class TabStripModel {
     CommandCloseTabsToRight,
     CommandRestoreTab,
     CommandTogglePinned,
+    CommandToggleTabAudioMuted,
     CommandBookmarkAllTabs,
     CommandSelectByDomain,
     CommandSelectByOpener,