RenderWidgetHostViewChildFrame's called a virtual in its ctor.

content/browser/renderer_host/render_widget_host_view_aura.h

Index: content/browser/renderer_host/render_widget_host_view_aura.h
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.h b/content/browser/renderer_host/render_widget_host_view_aura.h
index 53431c5dbaea63be11803ee3a5d5af662eed8bd8..0c10ef0b8304b5a3b159ca8013bd2f445e678a7b 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.h
+++ b/content/browser/renderer_host/render_widget_host_view_aura.h
@@ -532,6 +532,8 @@ class CONTENT_EXPORT RenderWidgetHostViewAura
   // Forwards a mouse event to this view's parent window delegate.
   void ForwardMouseEventToParent(ui::MouseEvent* event);
 
+  void UpdateNeedsBeginFramesInternal();
+
   // Returns the RenderViewHostDelegateView instance for this view. Returns
   // NULL on failure.
   RenderViewHostDelegateView* GetRenderViewHostDelegateView();
@@ -592,8 +594,13 @@ class CONTENT_EXPORT RenderWidgetHostViewAura
   // The begin frame source being observed.  Null if none.
   cc::BeginFrameSource* begin_frame_source_;
   cc::BeginFrameArgs last_begin_frame_args_;
+
+  // Whether a request for begin frames has been issued.
   bool needs_begin_frames_;
 
+  // Whether or not a frame observer has been added.
+  bool added_frame_observer_;
+
   // Used to record the last position of the mouse.
   // While the mouse is locked, they store the last known position just as mouse
   // lock was entered.