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

content/browser/frame_host/render_frame_host_impl.h

Index: content/browser/frame_host/render_frame_host_impl.h
diff --git a/content/browser/frame_host/render_frame_host_impl.h b/content/browser/frame_host/render_frame_host_impl.h
index db36975b359f33f3f9c83a0d6514e1a2f025edd8..2861fffe4c0f76706b26ed24973f54ead1153a61 100644
--- a/content/browser/frame_host/render_frame_host_impl.h
+++ b/content/browser/frame_host/render_frame_host_impl.h
@@ -247,6 +247,10 @@ class CONTENT_EXPORT RenderFrameHostImpl
   // after they are blocked in RenderWidgetHelper::CreateNewWindow.
   void Init();
 
+  // Returns true if the frame recently plays an audio.
+  bool IsAudible();

[DaleCurtis, 2017/06/22 00:35:54]

const? Prefer bool is_audible() const { return is_audible_; } for consistency
with the other hacker_style() accessors here.

[lpy, 2017/06/22 02:28:52]

Done.

+  void OnAudioStateChanged(bool audible);
+
   int routing_id() const { return routing_id_; }
 
   // Called when this frame has added a child. This is a continuation of an IPC
@@ -1182,6 +1186,9 @@ class CONTENT_EXPORT RenderFrameHostImpl
   // If true, then the RenderFrame has selected text.
   bool has_selection_;
 
+  // If true, then the RenderFrame is playing audio.
+  bool is_audible_;
+
   // PlzNavigate: The Previews state of the last navigation. This is used during
   // history navigation of subframes to ensure that subframes navigate with the
   // same Previews status as the top-level frame.