Allow objects without scrollbars to be scrollable

Source/core/rendering/RenderLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 1311 matching lines @@
     }
 
     return 0;
 }
 
 IntRect RenderLayer::scrollableAreaBoundingBox() const
 {
     return renderer()->absoluteBoundingBoxRect();
 }
 
+bool RenderLayer::isHorizontallyScrollable() const
+{
+    RenderBox* box = renderBox();
+    ASSERT(box);
+
+    EOverflow overflowStyle = renderer()->style()->overflowX();
+    return (overflowStyle == OSCROLL || overflowStyle == OAUTO);
+}
+
+bool RenderLayer::isVerticallyScrollable() const
+{
+    RenderBox* box = renderBox();
+    ASSERT(box);
+
+    EOverflow overflowStyle = renderer()->style()->overflowY();
+    return (overflowStyle == OSCROLL || overflowStyle == OAUTO);
+}
+
 RenderLayer* RenderLayer::enclosingTransformedAncestor() const
 {
     RenderLayer* curr = parent();
     while (curr && !curr->isRootLayer() && !curr->transform())
         curr = curr->parent();
 
     return curr;
 }
 
 static inline const RenderLayer* compositingContainer(const RenderLayer* layer)
@@ skipping 1140 matching lines @@
         styledElement->setInlineStyleProperty(CSSPropertyHeight, String::number(roundToInt(baseHeight + difference.height())) + "px", false);
     }
 
     document->updateLayout();
 
     // FIXME (Radar 4118564): We should also autoscroll the window as necessary to keep the point under the cursor in view.
 }
 
 int RenderLayer::scrollSize(ScrollbarOrientation orientation) const
 {
-    Scrollbar* scrollbar = ((orientation == HorizontalScrollbar) ? m_hBar : m_vBar).get();
-    return scrollbar ? (scrollbar->totalSize() - scrollbar->visibleSize()) : 0;
+    RenderBox* box = renderBox();
+    ASSERT(box);
+
+    if (orientation == HorizontalScrollbar)
+        return m_scrollSize.width() - box->pixelSnappedClientWidth();
+
+    return m_scrollSize.height() - box->pixelSnappedClientHeight();
 }
 
 int RenderLayer::scrollPosition(Scrollbar* scrollbar) const
 {
     if (scrollbar->orientation() == HorizontalScrollbar)
         return scrollXOffset();
     if (scrollbar->orientation() == VerticalScrollbar)
         return scrollYOffset();
     return 0;
 }
@@ skipping 349 matching lines @@
             willRemoveHorizontalScrollbar(scrollbar.get());
         else
             willRemoveVerticalScrollbar(scrollbar.get());
     }
 
     scrollbar->removeFromParent();
     scrollbar->disconnectFromScrollableArea();
     scrollbar = 0;
 }
 
-bool RenderLayer::scrollsOverflow() const
-{
-    if (!renderer()->isBox())
-        return false;
-
-    return toRenderBox(renderer())->scrollsOverflow();
-}
-
 void RenderLayer::setHasHorizontalScrollbar(bool hasScrollbar)
 {
     if (hasScrollbar == hasHorizontalScrollbar())
         return;
 
     if (hasScrollbar)
         m_hBar = createScrollbar(HorizontalScrollbar);
     else
         destroyScrollbar(HorizontalScrollbar);
 
@@ skipping 3516 matching lines @@
     }
 }
 
 void showLayerTree(const WebCore::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif