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

chrome/browser/ui/tabs/tab_strip_model_observer.h

Index: chrome/browser/ui/tabs/tab_strip_model_observer.h
diff --git a/chrome/browser/ui/tabs/tab_strip_model_observer.h b/chrome/browser/ui/tabs/tab_strip_model_observer.h
index 210a2c0621dde698754eac9ed780a6b7ac341030..b6810e955550dc4b5ea59cee9a7aa67a5343e2e5 100644
--- a/chrome/browser/ui/tabs/tab_strip_model_observer.h
+++ b/chrome/browser/ui/tabs/tab_strip_model_observer.h
@@ -5,6 +5,8 @@
 #ifndef CHROME_BROWSER_UI_TABS_TAB_STRIP_MODEL_OBSERVER_H_
 #define CHROME_BROWSER_UI_TABS_TAB_STRIP_MODEL_OBSERVER_H_
 
+#include <string>
+
 class TabStripModel;
 
 namespace content {
@@ -129,6 +131,13 @@ class TabStripModelObserver {
   // TabMiniStateChanged as to how this relates to TabMiniStateChanged.
   virtual void TabPinnedStateChanged(content::WebContents* contents, int index);
 
+  // Invoked when the audible or muted states change.
+  virtual void TabAudibleStateChanged(content::WebContents* contents,

[sky, 2015/02/02 15:43:06]

I don't think this makes sense in the TabStripModel. Why put it here?

+                                      bool audible);
+  virtual void TabMutedStateChanged(content::WebContents* contents,
+                                    bool muted,
+                                    const std::string& cause);
+
   // Invoked if the mini state of a tab changes.
   // NOTE: This is sent when the pinned state of a non-app tab changes and is
   // sent in addition to TabPinnedStateChanged. UI code typically need not care