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 b88fca74e0475775ae26bbb4ae1f2a525979d9a3..db8fd098f479e82104789e33804614f2498cf033 100644
--- a/Source/core/rendering/RenderLayer.h
+++ b/Source/core/rendering/RenderLayer.h
@@ -407,14 +407,6 @@ 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(); }
 
@@ -426,7 +418,6 @@ 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;
@@ -827,6 +818,14 @@ 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.
@@ -1000,8 +999,6 @@ private:
 
     bool shouldBeSelfPaintingLayer() const;
 
-    int scrollPosition(Scrollbar*) const;
-
     // ScrollableArea interface
     virtual void invalidateScrollbarRect(Scrollbar*, const IntRect&);
     virtual void invalidateScrollCornerRect(const IntRect&);
@@ -1026,6 +1023,8 @@ 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;
@@ -1094,11 +1093,6 @@ private:
     friend class RenderLayerCompositor;
     friend class RenderLayerModelObject;
 
-    LayoutUnit overflowTop() const;
-    LayoutUnit overflowBottom() const;
-    LayoutUnit overflowLeft() const;
-    LayoutUnit overflowRight() const;
-
     IntRect rectForHorizontalScrollbar(const IntRect& borderBoxRect) const;
     IntRect rectForVerticalScrollbar(const IntRect& borderBoxRect) const;
 
@@ -1201,7 +1195,7 @@ 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;