Allow objects without scrollbars to be scrollable

Source/core/platform/Scrollbar.h

 /*
  * Copyright (C) 2004, 2006 Apple Computer, 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 67 matching lines @@
     virtual bool isCustomScrollbar() const { return false; }
     virtual ScrollbarOrientation orientation() const { return m_orientation; }
 
     virtual int value() const { return lroundf(m_currentPos); }
     virtual float currentPos() const { return m_currentPos; }
     virtual int visibleSize() const { return m_visibleSize; }
     virtual int totalSize() const { return m_totalSize; }
     virtual int maximum() const { return m_totalSize - m_visibleSize; }
     virtual ScrollbarControlSize controlSize() const { return m_controlSize; }
 
-    virtual int lineStep() const { return m_lineStep; }
-    virtual int pageStep() const { return m_pageStep; }
-
     virtual ScrollbarPart pressedPart() const { return m_pressedPart; }
     virtual ScrollbarPart hoveredPart() const { return m_hoveredPart; }
 
     virtual void styleChanged() { }
 
     virtual bool enabled() const { return m_enabled; }
     virtual void setEnabled(bool);
 
     // Called by the ScrollableArea when the scroll offset changes.
     void offsetDidChange();
 
-    static int pixelsPerLineStep() { return 40; }
-    static float minFractionToStepWhenPaging() { return 0.875f; }
-    static int maxOverlapBetweenPages();
-
     void disconnectFromScrollableArea() { m_scrollableArea = 0; }
     ScrollableArea* scrollableArea() const { return m_scrollableArea; }
 
     int pressedPos() const { return m_pressedPos; }
 
-    float pixelStep() const { return m_pixelStep; }
-
     virtual void setHoveredPart(ScrollbarPart);
     virtual void setPressedPart(ScrollbarPart);
 
-    void setSteps(int lineStep, int pageStep, int pixelsPerStep = 1);
     void setProportion(int visibleSize, int totalSize);
     void setPressedPos(int p) { m_pressedPos = p; }
 
     virtual void paint(GraphicsContext*, const IntRect& damageRect);
 
     virtual bool isOverlayScrollbar() const;
     bool shouldParticipateInHitTesting();
 
     bool isWindowActive() const;
 
@@ skipping 44 matching lines @@
 
     ScrollableArea* m_scrollableArea;
     ScrollbarOrientation m_orientation;
     ScrollbarControlSize m_controlSize;
     ScrollbarTheme* m_theme;
 
     int m_visibleSize;
     int m_totalSize;
     float m_currentPos;
     float m_dragOrigin;
-    int m_lineStep;
-    int m_pageStep;
-    float m_pixelStep;
 
     ScrollbarPart m_hoveredPart;
     ScrollbarPart m_pressedPart;
     int m_pressedPos;
     float m_scrollPos;
     bool m_draggingDocument;
     int m_documentDragPos;
 
     bool m_enabled;
 
     Timer<Scrollbar> m_scrollTimer;
     bool m_overlapsResizer;
 
     bool m_suppressInvalidation;
 
     bool m_isAlphaLocked;
 
 private:
     virtual bool isScrollbar() const { return true; }
     virtual AXObjectCache* existingAXObjectCache() const;
+
+    float scrollableAreaCurrentPos() const;
 };
 
 } // namespace WebCore
 
 #endif // Scrollbar_h