Fixed the audio backgrounding bug

content/browser/renderer_host/render_process_host_impl.cc

Index: content/browser/renderer_host/render_process_host_impl.cc
diff --git a/content/browser/renderer_host/render_process_host_impl.cc b/content/browser/renderer_host/render_process_host_impl.cc
index 3471e3c087df2e43716a1bd742defd22d7326c79..6b065927239f147f709dab5723974a490b4883d7 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -1092,6 +1092,28 @@ int RenderProcessHostImpl::VisibleWidgetCount() const {
   return visible_widgets_;
 }
 
+void RenderProcessHostImpl::AudioStopped() {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+
+  // If the backgrounding was skipped because audio was playing, we background

[gab, 2015/06/30 13:41:41]

-we (in general we try to avoid "we" in comments), e.g.

// If backgrounding was skipped because audio was playing, background the tab
now.

[sebsg, 2015/07/02 12:58:08]

Done.

+  // the tab.
+  if (backgrounded_)
+    SetBackgrounded(true);
+}
+
+void RenderProcessHostImpl::AudioStarted() {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+
+  // If audio starts from a backgrounded tab, we un-background it.

[gab, 2015/06/30 13:41:41]

// If audio starts playing from a backgrounded tab, unbackground it.

[sebsg, 2015/07/02 12:58:08]

Done.

+  if (backgrounded_) {
+    SetBackgrounded(false);
+
+    // Since it's not a visible tab, we need to set it to backgrounded so that
+    // it is backgrounded again when the video finishes.

[gab, 2015/06/30 13:41:41]

// Since it's not a visible tab, it needs to be marked for backgrounding again
so that it is re-backgrounded if/when the audio stops.

[sebsg, 2015/07/02 12:58:09]

Done.

+    SetBackgrounded(true);
+  }
+}
+
 bool RenderProcessHostImpl::IsForGuestsOnly() const {
   return is_for_guests_only_;
 }
@@ -2237,6 +2259,7 @@ void RenderProcessHostImpl::SuddenTerminationChanged(bool enabled) {
 }
 
 void RenderProcessHostImpl::SetBackgrounded(bool backgrounded) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
   TRACE_EVENT1("renderer_host", "RenderProcessHostImpl::SetBackgrounded",
                "backgrounded", backgrounded);
   // Note: we always set the backgrounded_ value.  If the process is NULL