Use a boolean hasCompositedLayerMapping() accessor instead of the pointer

Source/core/rendering/RenderLayerScrollableArea.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 132 matching lines @@
     if (RenderBox* enclosingScrollableBox = m_box->enclosingScrollableBox())
         return enclosingScrollableBox->layer()->scrollableArea();
 
     // FIXME: We should return the frame view here (or possibly an ancestor frame view,
     // if the frame view isn't scrollable.
     return 0;
 }
 
 GraphicsLayer* RenderLayerScrollableArea::layerForScrolling() const
 {
-    return m_box->compositedLayerMapping() ? m_box->compositedLayerMapping()->scrollingContentsLayer() : 0;
+    return m_box->hasCompositedLayerMapping() ? m_box->compositedLayerMapping()->scrollingContentsLayer() : 0;
 }
 
 GraphicsLayer* RenderLayerScrollableArea::layerForHorizontalScrollbar() const
 {
-    return m_box->compositedLayerMapping() ? m_box->compositedLayerMapping()->layerForHorizontalScrollbar() : 0;
+    return m_box->hasCompositedLayerMapping() ? m_box->compositedLayerMapping()->layerForHorizontalScrollbar() : 0;
 }
 
 GraphicsLayer* RenderLayerScrollableArea::layerForVerticalScrollbar() const
 {
-    return m_box->compositedLayerMapping() ? m_box->compositedLayerMapping()->layerForVerticalScrollbar() : 0;
+    return m_box->hasCompositedLayerMapping() ? m_box->compositedLayerMapping()->layerForVerticalScrollbar() : 0;
 }
 
 GraphicsLayer* RenderLayerScrollableArea::layerForScrollCorner() const
 {
-    return m_box->compositedLayerMapping() ? m_box->compositedLayerMapping()->layerForScrollCorner() : 0;
+    return m_box->hasCompositedLayerMapping() ? m_box->compositedLayerMapping()->layerForScrollCorner() : 0;
 }
 
 void RenderLayerScrollableArea::invalidateScrollbarRect(Scrollbar* scrollbar, const IntRect& rect)
 {
     if (scrollbar == m_vBar.get()) {
         if (GraphicsLayer* layer = layerForVerticalScrollbar()) {
             layer->setNeedsDisplayInRect(rect);
             return;
         }
     } else {
@@ skipping 701 matching lines @@
     const IntRect& scrollCorner = scrollCornerRect();
     if (m_scrollCorner)
         m_scrollCorner->setFrameRect(scrollCorner);
 
     if (m_resizer)
         m_resizer->setFrameRect(resizerCornerRect(borderBox, ResizerForPointer));
 
     // FIXME, this should eventually be removed, once we are certain that composited
     // controls get correctly positioned on a compositor update. For now, conservatively
     // leaving this unchanged.
-    if (m_box->compositedLayerMapping())
+    if (m_box->hasCompositedLayerMapping())
         m_box->compositedLayerMapping()->positionOverflowControlsLayers(offsetFromRoot);
 }
 
 bool RenderLayerScrollableArea::scrollsOverflow() const
 {
     if (FrameView* frameView = m_box->view()->frameView())
         return frameView->containsScrollableArea(this);
 
     return false;
 }
@@ skipping 531 matching lines @@
             compositor->updateCompositingLayers(CompositingUpdateOnScroll);
     }
 }
 
 bool RenderLayerScrollableArea::usesCompositedScrolling() const
 {
     // Scroll form controls on the main thread so they exhibit correct touch scroll event bubbling
     if (m_box && (m_box->isIntristicallyScrollable(VerticalScrollbar) || m_box->isIntristicallyScrollable(HorizontalScrollbar)))
         return false;
 
-    return m_box->compositedLayerMapping() && m_box->compositedLayerMapping()->scrollingLayer();
+    return m_box->hasCompositedLayerMapping() && m_box->compositedLayerMapping()->scrollingLayer();
 }
 
 bool RenderLayerScrollableArea::adjustForForceCompositedScrollingMode(bool value) const
 {
     switch (m_forceNeedsCompositedScrolling) {
     case DoNotForceCompositedScrolling:
         return value;
     case CompositedScrollingAlwaysOn:
         return true;
     case CompositedScrollingAlwaysOff:
@@ skipping 12 matching lines @@
 void RenderLayerScrollableArea::setForceNeedsCompositedScrolling(ForceNeedsCompositedScrollingMode mode)
 {
     if (m_forceNeedsCompositedScrolling == mode)
         return;
 
     m_forceNeedsCompositedScrolling = mode;
     layer()->didUpdateNeedsCompositedScrolling();
 }
 
 } // Namespace WebCore