Remove dead paint flush tracking code.

content/renderer/render_widget_owner_delegate.h

Index: content/renderer/render_widget_owner_delegate.h
diff --git a/content/renderer/render_widget_owner_delegate.h b/content/renderer/render_widget_owner_delegate.h
index c5ad92f826126596e7f64919085c01daaac2ff8d..ad60e65692d15f87e6ad565ed9f38afadb7de6a7 100644
--- a/content/renderer/render_widget_owner_delegate.h
+++ b/content/renderer/render_widget_owner_delegate.h
@@ -39,10 +39,6 @@ class CONTENT_EXPORT RenderWidgetOwnerDelegate {
   virtual bool RenderWidgetWillHandleMouseEvent(
       const blink::WebMouseEvent& event) = 0;
 
-  // Painting notifications. DidFlushPaint happens once we've received the ACK
-  // that the screen has been updated.
-  virtual void RenderWidgetDidFlushPaint() = 0;
-
  protected:
   virtual ~RenderWidgetOwnerDelegate() {}
 };