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

chrome/browser/ui/tabs/tab_utils.h

 // Copyright (c) 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.
 
 #ifndef CHROME_BROWSER_UI_TABS_TAB_UTILS_H_
 #define CHROME_BROWSER_UI_TABS_TAB_UTILS_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/string16.h"
 
 namespace content {
 class WebContents;
 }  // namespace content
 
 namespace gfx {
 class Animation;
 class Image;
 }  // namespace gfx
 
 // Media state for a tab.  In reality, more than one of these may apply.  See
 // comments for GetTabMediaStateForContents() below.
 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 {
 
 // Logic to determine which components (i.e., close button, favicon, and media
 // indicator) of a tab should be shown, given current state.  |capacity|
 // specifies how many components can be shown, given available tab width.
 //
 // Precedence rules for deciding what to show when capacity is insufficient to
 // show everything:
@@ skipping 23 matching lines @@
 
 // Returns the media state to be shown by the tab's media indicator.  When
 // multiple states apply (e.g., tab capture with audio playback), the one most
 // relevant to user privacy concerns is selected.
 TabMediaState GetTabMediaStateForContents(content::WebContents* contents);
 
 // Returns a cached image, to be shown by the media indicator for the given
 // |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
 // has started/stopped.
 scoped_ptr<gfx::Animation> CreateTabMediaIndicatorFadeAnimation(
     TabMediaState next_media_state);
 
 // Returns the text to show in a tab's tooltip: The contents |title|, followed
 // by a break, followed by a localized string describing the |media_state|.
 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_