Allow objects without scrollbars to be scrollable

Source/core/rendering/RenderLayer.h

Index: Source/core/rendering/RenderLayer.h
diff --git a/Source/core/rendering/RenderLayer.h b/Source/core/rendering/RenderLayer.h
index 89c41e6fafa02086a63b0c0102594ad21414a711..22537e965baf648778bf9781363df6ef5dd523bf 100644
--- a/Source/core/rendering/RenderLayer.h
+++ b/Source/core/rendering/RenderLayer.h
@@ -456,14 +456,6 @@ public:
 
     LayoutRect getRectToExpose(const LayoutRect& visibleRect, const LayoutRect& exposeRect, const ScrollAlignment& alignX, const ScrollAlignment& alignY);
 
-    bool scrollsOverflow() const;
-    bool hasScrollbars() const { return m_hBar || m_vBar; }
-    void setHasHorizontalScrollbar(bool);
-    void setHasVerticalScrollbar(bool);
-
-    PassRefPtr<Scrollbar> createScrollbar(ScrollbarOrientation);
-    void destroyScrollbar(ScrollbarOrientation);
-
     bool hasHorizontalScrollbar() const { return horizontalScrollbar(); }
     bool hasVerticalScrollbar() const { return verticalScrollbar(); }
 
@@ -475,7 +467,6 @@ public:
     int verticalScrollbarWidth(OverlayScrollbarSizeRelevancy = IgnoreOverlayScrollbarSize) const;
     int horizontalScrollbarHeight(OverlayScrollbarSizeRelevancy = IgnoreOverlayScrollbarSize) const;
 
-    bool hasOverflowControls() const;
     // isPointInResizeControl() is used for testing if a pointer/touch position is in the resize control
     // area.
     bool isPointInResizeControl(const IntPoint& absolutePoint, ResizerHitTestType resizerHitTestType) const;
@@ -881,6 +872,14 @@ private:
         OnlyStackingContextsCanBeStackingContainers
     };
 
+    void setHasHorizontalScrollbar(bool);
+    void setHasVerticalScrollbar(bool);
+
+    PassRefPtr<Scrollbar> createScrollbar(ScrollbarOrientation);
+    void destroyScrollbar(ScrollbarOrientation);
+
+    bool hasOverflowControls() const;
+
     void updateZOrderLists();
     void rebuildZOrderLists();
     // See the comment for collectLayers for information about the layerToForceAsStackingContainer parameter.
@@ -1054,8 +1053,6 @@ private:
 
     bool shouldBeSelfPaintingLayer() const;
 
-    int scrollPosition(Scrollbar*) const;
-    
     // ScrollableArea interface
     virtual void invalidateScrollbarRect(Scrollbar*, const IntRect&);
     virtual void invalidateScrollCornerRect(const IntRect&);
@@ -1080,6 +1077,8 @@ private:
     virtual bool shouldSuspendScrollAnimations() const;
     virtual bool scrollbarsCanBeActive() const;
     virtual IntRect scrollableAreaBoundingBox() const OVERRIDE;
+    virtual bool userInputScrollable(ScrollbarOrientation) const OVERRIDE;
+    virtual int pageStep(ScrollbarOrientation) const OVERRIDE;
 
     // Rectangle encompassing the scroll corner and resizer rect.
     IntRect scrollCornerAndResizerRect() const;
@@ -1151,11 +1150,6 @@ private:
     // Only safe to call from RenderBoxModelObject::destroyLayer(RenderArena*)
     void destroy(RenderArena*);
 
-    LayoutUnit overflowTop() const;
-    LayoutUnit overflowBottom() const;
-    LayoutUnit overflowLeft() const;
-    LayoutUnit overflowRight() const;
-
     IntRect rectForHorizontalScrollbar(const IntRect& borderBoxRect) const;
     IntRect rectForVerticalScrollbar(const IntRect& borderBoxRect) const;
 
@@ -1258,7 +1252,7 @@ protected:
     IntSize m_scrollOffset;
 
     // The width/height of our scrolled area.
-    LayoutSize m_scrollSize;
+    LayoutRect m_overflowRect;
 
     // For layers with overflow, we have a pair of scrollbars.
     RefPtr<Scrollbar> m_hBar;