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

chrome/browser/ui/tabs/tab_utils.cc

 // 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.
 
 #include "chrome/browser/ui/tabs/tab_utils.h"
 
 #include "base/command_line.h"
 #include "base/strings/string16.h"
 #include "chrome/browser/media/media_capture_devices_dispatcher.h"
 #include "chrome/browser/media/media_stream_capture_indicator.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/grit/generated_resources.h"
 #include "content/public/browser/web_contents.h"
 #include "grit/theme_resources.h"
 #include "ui/base/l10n/l10n_util.h"
 #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 {
 
 // Interval between frame updates of the tab indicator animations.  This is not
 // the usual 60 FPS because a trade-off must be made between tab UI animation
 // smoothness and media recording/playback performance on low-end hardware.
 const int kIndicatorFrameIntervalMs = 50;  // 20 FPS
 
 // Fade-in/out duration for the tab indicator animations.  Fade-in is quick to
@@ skipping 215 matching lines @@
     case TAB_MEDIA_STATE_AUDIO_MUTING:
       return IsTabAudioMutingFeatureEnabled();
     case TAB_MEDIA_STATE_RECORDING:
     case TAB_MEDIA_STATE_CAPTURING:
       return false;
   }
   NOTREACHED();
   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) {
   return contents && contents->IsAudioMuted();
 }
 
 bool AreAllTabsMuted(const TabStripModel& tab_strip,
                      const std::vector<int>& indices) {
   for (std::vector<int>::const_iterator i = indices.begin(); i != indices.end();
        ++i) {
     if (!IsTabAudioMuted(tab_strip.GetWebContentsAt(*i)))
       return false;
   }
   return true;
 }
 
 }  // namespace chrome