Define frame subscription interface and implementation on Mac

content/port/browser/render_widget_host_view_port.h

Index: content/port/browser/render_widget_host_view_port.h
diff --git a/content/port/browser/render_widget_host_view_port.h b/content/port/browser/render_widget_host_view_port.h
index f80ea2408fb818973ab2b97fe7ba93d554f18eb8..adb50881c259e010ddd6426113f2eb17c6b66915 100644
--- a/content/port/browser/render_widget_host_view_port.h
+++ b/content/port/browser/render_widget_host_view_port.h
@@ -42,6 +42,7 @@ struct WebScreenInfo;
 
 namespace content {
 class BackingStore;
+class RenderWidgetHostViewFrameSubscriber;
 class SmoothScrollGesture;
 struct NativeWebKeyboardEvent;
 
@@ -188,6 +189,21 @@ class CONTENT_EXPORT RenderWidgetHostViewPort : public RenderWidgetHostView {
   // IsSurfaceAvailableForCopy() and HasAcceleratedSurface().
   virtual bool CanCopyToVideoFrame() const = 0;
 
+  // Return true if frame subscription is supported on this platform.
+  virtual bool CanSubscribeFrame() const { return false; }

[piman, 2013/02/22 20:45:47]

note: all methods in this class are pure virtual. You can move the default
implementations to RenderWidgetHostViewBase

[Alpha Left Google, 2013/02/22 21:05:38]

Okay will do.

+
+  // Begin subscribing for presentation events and captured frames.
+  // |subscriber| is now owned by this object, it will be called only on the
+  // UI thread.
+  //
+  // TODO(hclam): Implement this API on all platforms.
+  virtual void BeginFrameSubscription(
+      RenderWidgetHostViewFrameSubscriber* subscriber) {}
+
+  // End subscribing for frame presentation events. FrameSubscriber will be
+  // deleted after this call.
+  virtual void EndFrameSubscription() {}
+
   // Called when accelerated compositing state changes.
   virtual void OnAcceleratedCompositingStateChange() = 0;
   // |params.window| and |params.surface_id| indicate which accelerated