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

content/browser/web_contents/web_contents_impl.cc

Index: content/browser/web_contents/web_contents_impl.cc
diff --git a/content/browser/web_contents/web_contents_impl.cc b/content/browser/web_contents/web_contents_impl.cc
index 5ec31a02c05612ac3f3807e8b0e0ed9d560352f4..b1300e2c162eab7375943ee033fac7d3863281a2 100644
--- a/content/browser/web_contents/web_contents_impl.cc
+++ b/content/browser/web_contents/web_contents_impl.cc
@@ -331,7 +331,8 @@ WebContentsImpl::WebContentsImpl(BrowserContext* browser_context,
       geolocation_service_context_(new GeolocationServiceContext()),
       accessibility_mode_(
           BrowserAccessibilityStateImpl::GetInstance()->accessibility_mode()),
-      audio_stream_monitor_(this),
+      audio_stream_monitor_(base::Bind(
+          &WebContentsImpl::NotifyAudibleStateChanged, base::Unretained(this))),
       loading_weak_factory_(this) {
   for (size_t i = 0; i < g_created_callbacks.Get().size(); i++)
     g_created_callbacks.Get().at(i).Run(this);
@@ -949,14 +950,16 @@ bool WebContentsImpl::IsAudioMuted() const {
   return audio_muter_.get() && audio_muter_->is_muting();
 }
 
-void WebContentsImpl::SetAudioMuted(bool mute) {
-  DVLOG(1) << "SetAudioMuted(mute=" << mute << "), was " << IsAudioMuted()
+void WebContentsImpl::SetAudioMuted(bool muted, const std::string& cause) {
+  DVLOG(1) << "SetAudioMuted(muted=" << muted << ", cause =" << cause << "), was " << IsAudioMuted()
            << " for WebContentsImpl@" << this;
 
-  if (mute == IsAudioMuted())
+  if (muted == IsAudioMuted())
     return;
 
-  if (mute) {
+  NotifyMutedStateChanged(muted, cause);
+
+  if (muted) {
     if (!audio_muter_)
       audio_muter_.reset(new WebContentsAudioMuter(this));
     audio_muter_->StartMuting();
@@ -995,20 +998,30 @@ bool WebContentsImpl::IsBeingDestroyed() const {
 
 void WebContentsImpl::NotifyNavigationStateChanged(
     InvalidateTypes changed_flags) {
+  if (delegate_)
+    delegate_->NavigationStateChanged(this, changed_flags);
+}
+
+void WebContentsImpl::NotifyAudibleStateChanged(bool is_audible) {
+  DCHECK(AudioStreamMonitor::monitoring_available());
+
   // Create and release the audio power save blocker depending on whether the
   // tab is actively producing audio or not.
-  if (changed_flags == INVALIDATE_TYPE_TAB &&
-      AudioStreamMonitor::monitoring_available()) {
-    if (WasRecentlyAudible()) {
-      if (!audio_power_save_blocker_)
-        CreateAudioPowerSaveBlocker();
-    } else {
-      audio_power_save_blocker_.reset();
-    }
+  if (WasRecentlyAudible()) {
+    if (!audio_power_save_blocker_)
+      CreateAudioPowerSaveBlocker();
+  } else {
+    audio_power_save_blocker_.reset();
   }
 
-  if (delegate_)
-    delegate_->NavigationStateChanged(this, changed_flags);
+  // TODO: The following should be eliminated once the browser UI uses the new WebContentsObserver interface.

[miu, 2014/12/05 23:46:48]

Actually, I think I gave you bad advice (earlier) on having this TODO comment
here.  I need to first discuss this issue with the browser UI owners some more,
to decide whether NotifyNavigationStateChanged() is the right or wrong mechanism
to update the tab strip UI.  (Maybe the mechanism is right, and the method
should just be renamed to something better.)

In other words, for now, please replace this TODO comment with:

  // Notify the delegate that a UI update may be needed for the new tab media
state.

+  NotifyNavigationStateChanged(INVALIDATE_TYPE_TAB);
+
+  FOR_EACH_OBSERVER(WebContentsObserver, observers_, TabAudible(is_audible));
+}
+
+void WebContentsImpl::NotifyMutedStateChanged(bool is_muted, const std::string& cause) {
+  FOR_EACH_OBSERVER(WebContentsObserver, observers_, TabMuted(is_muted, cause));
 }
 
 base::TimeTicks WebContentsImpl::GetLastActiveTime() const {