Make tab audible and muted states and cause available for an extension API

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 4480a41609f149cbc48f01466975e4358718eaa5..dedee37534231d68025cc3bf5dcf15a59ed4be95 100644
--- a/chrome/browser/ui/tabs/tab_utils.h
+++ b/chrome/browser/ui/tabs/tab_utils.h
@@ -5,10 +5,12 @@
 #ifndef CHROME_BROWSER_UI_TABS_TAB_UTILS_H_
 #define CHROME_BROWSER_UI_TABS_TAB_UTILS_H_
 
+#include <string>
 #include <vector>
 
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/string16.h"
+#include "content/public/browser/web_contents_user_data.h"
 
 class TabStripModel;
 
@@ -33,6 +35,11 @@ enum TabMediaState {
 
 namespace chrome {
 
+// String to indicate reason for muted state change (user, capture, extension
+// id, or empty string)
+const char kMutedToggleCauseUser[] = "user";
+const char kMutedToggleCauseCapture[] = "auto-forced for capture";
+
 // 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.
@@ -99,7 +106,12 @@ bool CanToggleAudioMute(content::WebContents* contents);
 
 // Indicates/Sets whether all audio output from |contents| is muted.
 bool IsTabAudioMuted(content::WebContents* contents);
-void SetTabAudioMuted(content::WebContents* contents, bool mute);
+void SetTabAudioMuted(content::WebContents* contents,
+                      bool muted,
+                      const std::string& cause);
+
+// Get cause of mute (extensionid, kMutedToggleCause constant, or empty string)
+std::string& GetTabAudioMutedCause(content::WebContents* contents);

[miu, 2015/01/22 00:55:23]

Please make the return type const std::string& to avoid external mutation of the
string.

 
 // Returns true if the tabs at the |indices| in |tab_strip| are all muted.
 bool AreAllTabsMuted(const TabStripModel& tab_strip,