Maintain minimal error response.

content/public/browser/render_widget_host.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_PUBLIC_BROWSER_RENDER_WIDGET_HOST_H_
 #define CONTENT_PUBLIC_BROWSER_RENDER_WIDGET_HOST_H_
 
 #include "base/callback.h"
 #include "content/common/content_export.h"
 #include "content/public/browser/native_web_keyboard_event.h"
@@ skipping 231 matching lines @@
       const KeyPressEventCallback& callback) = 0;
 
   // Add/remove a callback that can handle all kinds of mouse events.
   typedef base::Callback<bool(const blink::WebMouseEvent&)> MouseEventCallback;
   virtual void AddMouseEventCallback(const MouseEventCallback& callback) = 0;
   virtual void RemoveMouseEventCallback(const MouseEventCallback& callback) = 0;
 
   // Get the screen info corresponding to this render widget.
   virtual void GetWebScreenInfo(blink::WebScreenInfo* result) = 0;
 
-  virtual SkColorType PreferredReadbackFormat() = 0;
-
  protected:
   friend class RenderWidgetHostImpl;
 
   // Retrieves the implementation class.  Intended only for code
   // within content/.  This method is necessary because
   // RenderWidgetHost is the root of a diamond inheritance pattern, so
   // subclasses inherit it virtually, which removes our ability to
   // static_cast to the subclass.
   virtual RenderWidgetHostImpl* AsRenderWidgetHostImpl() = 0;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_BROWSER_RENDER_WIDGET_HOST_H_