Factor painting code from RenderLayerScrollableArea into ScrollableAreaPainter

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 1452 matching lines @@
 void RenderLayer::updateScrollableArea()
 {
     if (requiresScrollableArea())
         m_scrollableArea = adoptPtr(new RenderLayerScrollableArea(*this));
     else
         m_scrollableArea = nullptr;
 }
 
 bool RenderLayer::hasOverflowControls() const
 {
-    return m_scrollableArea && (m_scrollableArea->hasScrollbar() || m_scrollableArea->hasScrollCorner() || renderer()->style()->resize() != RESIZE_NONE);
+    return m_scrollableArea && (m_scrollableArea->hasScrollbar() || m_scrollableArea->scrollCorner() || renderer()->style()->resize() != RESIZE_NONE);
 }
 
 void RenderLayer::collectFragments(LayerFragments& fragments, const RenderLayer* rootLayer, const LayoutRect& dirtyRect,
     ClipRectsCacheSlot clipRectsCacheSlot, OverlayScrollbarSizeRelevancy inOverlayScrollbarSizeRelevancy, ShouldRespectOverflowClip respectOverflowClip, const LayoutPoint* offsetFromRoot,
     const LayoutSize& subPixelAccumulation, const LayoutRect* layerBoundingBox)
 {
     if (!enclosingPaginationLayer() || hasTransformRelatedProperty()) {
         // For unpaginated layers, there is only one fragment.
         LayerFragment fragment;
         ClipRectsContext clipRectsContext(rootLayer, clipRectsCacheSlot, inOverlayScrollbarSizeRelevancy, subPixelAccumulation);
@@ skipping 1372 matching lines @@
     }
 }
 
 void showLayerTree(const blink::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif