[AudioStreamMonitor] Adds API to collect frame-level audibility.

content/browser/frame_host/render_frame_host_impl.cc

Index: content/browser/frame_host/render_frame_host_impl.cc
diff --git a/content/browser/frame_host/render_frame_host_impl.cc b/content/browser/frame_host/render_frame_host_impl.cc
index 47514f727c7221534c756cf7edf0585a7dd69657..bb9ac7469d96d9b0a37926b6617e468cca5a9498 100644
--- a/content/browser/frame_host/render_frame_host_impl.cc
+++ b/content/browser/frame_host/render_frame_host_impl.cc
@@ -454,6 +454,7 @@ RenderFrameHostImpl::RenderFrameHostImpl(SiteInstance* site_instance,
       pending_web_ui_type_(WebUI::kNoWebUI),
       should_reuse_web_ui_(false),
       has_selection_(false),
+      is_audible_(false),
       last_navigation_previews_state_(PREVIEWS_UNSPECIFIED),
       frame_host_interface_broker_binding_(this),
       frame_host_associated_binding_(this),
@@ -1012,6 +1013,9 @@ void RenderFrameHostImpl::RenderProcessGone(SiteInstanceImpl* site_instance) {
   // Any future UpdateState or UpdateTitle messages from this or a recreated
   // process should be ignored until the next commit.
   set_nav_entry_id(0);
+
+  if (is_audible_)
+    GetProcess()->OnAudioStreamRemoved();
 }
 
 void RenderFrameHostImpl::ReportContentSecurityPolicyViolation(
@@ -1199,6 +1203,16 @@ void RenderFrameHostImpl::Init() {
   }
 }
 
+void RenderFrameHostImpl::OnAudibleStateChanged(bool is_audible) {
+  if (is_audible_ == is_audible)
+    return;
+  if (is_audible)
+    GetProcess()->OnAudioStreamAdded();
+  else
+    GetProcess()->OnAudioStreamRemoved();
+  is_audible_ = is_audible;
+}
+
 void RenderFrameHostImpl::OnDidAddMessageToConsole(
     int32_t level,
     const base::string16& message,