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

chrome/browser/ui/tabs/tab_utils.h

Index: chrome/browser/ui/tabs/tab_utils.h
diff --git a/chrome/browser/ui/tabs/tab_utils.h b/chrome/browser/ui/tabs/tab_utils.h
index c11000bc44596eb9e06c8a790e2558bc4a8f2554..152fbdd2756e2ae74f1e5aa6f696ab135431493e 100644
--- a/chrome/browser/ui/tabs/tab_utils.h
+++ b/chrome/browser/ui/tabs/tab_utils.h
@@ -23,7 +23,8 @@ enum TabMediaState {
   TAB_MEDIA_STATE_NONE,
   TAB_MEDIA_STATE_RECORDING,  // Audio/Video being recorded, consumed by tab.
   TAB_MEDIA_STATE_CAPTURING,  // Tab contents being captured.
-  TAB_MEDIA_STATE_AUDIO_PLAYING  // Audible audio is playing from the tab.
+  TAB_MEDIA_STATE_AUDIO_PLAYING,  // Audible audio is playing from the tab.
+  TAB_MEDIA_STATE_AUDIO_MUTING,  // Tab audio is being muted.
 };
 
 namespace chrome {
@@ -67,6 +68,12 @@ TabMediaState GetTabMediaStateForContents(content::WebContents* contents);
 // |media_state|.  Uses the global ui::ResourceBundle shared instance.
 const gfx::Image& GetTabMediaIndicatorImage(TabMediaState media_state);
 
+// Returns the cached image, to be shown by the media indicator button for mouse
+// hover/pressed, when the indicator is in the given |media_state|.  Uses the
+// global ui::ResourceBundle shared instance.
+const gfx::Image& GetTabMediaIndicatorAffordanceImage(
+    TabMediaState media_state);
+
 // Returns a non-continuous Animation that performs a fade-in or fade-out
 // appropriate for the given |next_media_state|.  This is used by the tab media
 // indicator to alert the user that recording, tab capture, or audio playback
@@ -79,6 +86,13 @@ scoped_ptr<gfx::Animation> CreateTabMediaIndicatorFadeAnimation(
 base::string16 AssembleTabTooltipText(const base::string16& title,
                                       TabMediaState media_state);
 
+// Returns true if the experimental tab audio mute feature is enabled.
+bool IsTabAudioMutingFeatureEnabled();
+
+// Returns true if audio mute can be activated/deactivated for the given
+// |contents|.
+bool CanToggleAudioMute(content::WebContents* contents);
+
 }  // namespace chrome
 
 #endif  // CHROME_BROWSER_UI_TABS_TAB_UTILS_H_