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

chrome/common/chrome_switches.cc

Index: chrome/common/chrome_switches.cc
diff --git a/chrome/common/chrome_switches.cc b/chrome/common/chrome_switches.cc
index a04c81a0387450f8d957b7dc64dd0248b694ebe7..300e906c62e9798cd310e2bcb9791d2cc11b5a4f 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -615,6 +615,9 @@ const char kEnableSyncSyncedNotifications[] =
 // Enables synced articles.
 const char kEnableSyncArticles[]            = "enable-sync-articles";
 
+// Enables user control over muting tab audio from the tab strip.
+const char kEnableTabAudioMuting[]  = "enable-tab-audio-muting";
+
 // Enables fanciful thumbnail processing. Used with NTP for
 // instant-extended-api, where thumbnails are generally smaller.
 const char kEnableThumbnailRetargeting[]   = "enable-thumbnail-retargeting";