Remove dead paint flush tracking code.

content/renderer/render_widget.h

 // Copyright (c) 2012 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_H_
 #define CONTENT_RENDERER_RENDER_WIDGET_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 513 matching lines @@
   // go through OnResize.
   void AutoResizeCompositor();
 
   virtual void OnSetDeviceScaleFactor(float device_scale_factor);
   bool SetDeviceColorProfile(const std::vector<char>& color_profile);
 
   virtual void OnOrientationChange();
 
   // Override points to notify derived classes that a paint has happened.
   // DidInitiatePaint happens when that has completed, and subsequent rendering
-  // won't affect the painted content. DidFlushPaint happens once we've received
-  // the ACK that the screen has been updated. For a given paint operation,
-  // these overrides will always be called in the order DidInitiatePaint,
-  // DidFlushPaint.
+  // won't affect the painted content.
   virtual void DidInitiatePaint() {}
-  virtual void DidFlushPaint();
 
   virtual GURL GetURLForGraphicsContext3D();
 
   // Sets the "hidden" state of this widget.  All accesses to is_hidden_ should
   // use this method so that we can properly inform the RenderThread of our
   // state.
   void SetHidden(bool hidden);
 
   void DidToggleFullscreen();
 
@@ skipping 276 matching lines @@
   // Stores edit commands associated to the next key event.
   // Will be cleared as soon as the next key event is processed.
   EditCommands edit_commands_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidget);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_WIDGET_H_