Early terminate flings when scrolling impossible

Source/web/WebViewImpl.h

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 347 matching lines @@
     void mouseContextMenu(const WebMouseEvent&);
     void mouseDoubleClick(const WebMouseEvent&);
 
     bool detectContentOnTouch(const WebPoint&);
     bool startPageScaleAnimation(const WebCore::IntPoint& targetPosition, bool useAnchor, float newScale, double durationInSeconds);
 
     void numberOfWheelEventHandlersChanged(unsigned);
     void hasTouchEventHandlers(bool);
 
     // WebGestureCurveTarget implementation for fling.
-    virtual void scrollBy(const WebFloatSize&) OVERRIDE;
+    virtual bool scrollBy(const WebFloatSize& delta, const WebFloatSize& velocity) OVERRIDE;
+    virtual void scrollBy(const WebFloatSize& delta) OVERRIDE;
 
     // Handles context menu events orignated via the the keyboard. These
     // include the VK_APPS virtual key and the Shift+F10 combine. Code is
     // based on the Webkit function bool WebView::handleContextMenuEvent(WPARAM
     // wParam, LPARAM lParam) in webkit\webkit\win\WebView.cpp. The only
     // significant change in this function is the code to convert from a
     // Keyboard event to the Right Mouse button down event.
     bool sendContextMenuEvent(const WebKeyboardEvent&);
 
     // Notifies the WebView that a load has been committed. isNewNavigation
@@ skipping 391 matching lines @@
     float m_zoomFactorOverride;
 };
 
 // We have no ways to check if the specified WebView is an instance of
 // WebViewImpl because WebViewImpl is the only implementation of WebView.
 DEFINE_TYPE_CASTS(WebViewImpl, WebView, webView, true, true);
 
 } // namespace blink
 
 #endif