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

chrome/browser/ui/tabs/tab_utils.cc

Index: chrome/browser/ui/tabs/tab_utils.cc
diff --git a/chrome/browser/ui/tabs/tab_utils.cc b/chrome/browser/ui/tabs/tab_utils.cc
index a61996701309b28c8d94d985247a30ef396d64ae..ea1eaea927a1bd3e8d3341b085765988c1fd55c8 100644
--- a/chrome/browser/ui/tabs/tab_utils.cc
+++ b/chrome/browser/ui/tabs/tab_utils.cc
@@ -17,6 +17,17 @@
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/gfx/animation/multi_animation.h"
 
+struct LastMuteMetadata : public
+  content::WebContentsUserData<LastMuteMetadata> {

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

style: Please run `git cl format` to make indentation in-line with Chromium
style guide.

+      std::string cause;  // Extension ID or constant from header file
+                          // or empty string
+ private:
+      explicit LastMuteMetadata(content::WebContents* contents) {}
+      friend class content::WebContentsUserData<LastMuteMetadata>;
+};
+
+DEFINE_WEB_CONTENTS_USER_DATA_KEY(LastMuteMetadata);
+
 namespace chrome {
 
 namespace {
@@ -252,10 +263,26 @@ bool CanToggleAudioMute(content::WebContents* contents) {
   return false;
 }
 
-void SetTabAudioMuted(content::WebContents* contents, bool mute) {
+std::string& GetTabAudioMutedCause(content::WebContents* contents) {
+  LastMuteMetadata::CreateForWebContents(contents);  // Create if not exists.
+  if (GetTabMediaStateForContents(contents) == TAB_MEDIA_STATE_CAPTURING) {
+    // For tab capture, libcontent forces muting off.
+    LastMuteMetadata::FromWebContents(contents)->cause =
+  kMutedToggleCauseCapture;
+  }
+    return LastMuteMetadata::FromWebContents(contents)->cause;
+}
+
+void SetTabAudioMuted(content::WebContents* contents,
+                      bool muted,
+                      const std::string& cause) {
   if (!contents || !chrome::CanToggleAudioMute(contents))
     return;
-  contents->SetAudioMuted(mute);
+
+  LastMuteMetadata::CreateForWebContents(contents);  // Create if not exists.
+  LastMuteMetadata::FromWebContents(contents)->cause = cause;
+
+  contents->SetAudioMuted(muted);
 }
 
 bool IsTabAudioMuted(content::WebContents* contents) {