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..c010c92c6e33729743763ff9b82fbe4ec9b154f6 100644
--- a/chrome/browser/ui/tabs/tab_utils.cc
+++ b/chrome/browser/ui/tabs/tab_utils.cc
@@ -17,8 +17,22 @@
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/gfx/animation/multi_animation.h"
 
+struct LastMuteMetadata
+    : public content::WebContentsUserData<LastMuteMetadata> {
+  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 {
 
+const char kMutedToggleCauseUser[] = "user";
+const char kMutedToggleCauseCapture[] = "auto-forced for capture";
+
 namespace {
 
 // Interval between frame updates of the tab indicator animations.  This is not
@@ -252,9 +266,25 @@ bool CanToggleAudioMute(content::WebContents* contents) {
   return false;
 }
 
-void SetTabAudioMuted(content::WebContents* contents, bool mute) {
+const 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 mute,
+                      const std::string& cause) {
   if (!contents || !chrome::CanToggleAudioMute(contents))
     return;
+
+  LastMuteMetadata::CreateForWebContents(contents);  // Create if not exists.
+  LastMuteMetadata::FromWebContents(contents)->cause = cause;
+
   contents->SetAudioMuted(mute);
 }