Remove dead paint flush tracking code.

content/renderer/render_widget_owner_delegate.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_RENDERER_RENDER_WIDGET_OWNER_DELEGATE_H_
 #define CONTENT_RENDERER_RENDER_WIDGET_OWNER_DELEGATE_H_
 
 #include "content/common/content_export.h"
 
 namespace blink {
@@ skipping 21 matching lines @@
 
   // As in RenderWidgetInputHandlerDelegate.
   virtual void RenderWidgetFocusChangeComplete() = 0;
   virtual bool DoesRenderWidgetHaveTouchEventHandlersAt(
       const gfx::Point& point) const = 0;
   virtual bool RenderWidgetWillHandleGestureEvent(
       const blink::WebGestureEvent& event) = 0;
   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() {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_WIDGET_OWNER_DELEGATE_H_