Use a boolean hasCompositedLayerMapping() accessor instead of the pointer

Source/web/tests/ScrollingCoordinatorChromiumTest.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in the
@@ skipping 142 matching lines @@
 static WebLayer* webLayerFromElement(Element* element)
 {
     if (!element)
         return 0;
     RenderObject* renderer = element->renderer();
     if (!renderer || !renderer->isBoxModelObject())
         return 0;
     RenderLayer* layer = toRenderBoxModelObject(renderer)->layer();
     if (!layer)
         return 0;
+
+    if (!layer->hasCompositedLayerMapping())
+        return 0;
     CompositedLayerMapping* compositedLayerMapping = layer->compositedLayerMapping();
-    if (!compositedLayerMapping)
-        return 0;
+
     GraphicsLayer* graphicsLayer = compositedLayerMapping->mainGraphicsLayer();
     if (!graphicsLayer)
         return 0;
     return graphicsLayer->platformLayer();
 }
 
 TEST_F(ScrollingCoordinatorChromiumTest, fastScrollingForFixedPosition)
 {
     registerMockedHttpURLLoad("fixed-position.html");
     navigateTo(m_baseURL + "fixed-position.html");
@@ skipping 122 matching lines @@
     Element* scrollableElement = m_webViewImpl->mainFrameImpl()->frame()->document()->getElementById("scrollable");
     ASSERT(scrollableElement);
 
     RenderObject* renderer = scrollableElement->renderer();
     ASSERT_TRUE(renderer->isBox());
     ASSERT_TRUE(renderer->hasLayer());
 
     RenderBox* box = toRenderBox(renderer);
     ASSERT_TRUE(box->usesCompositedScrolling());
     ASSERT_EQ(PaintsIntoOwnBacking, box->layer()->compositingState());
+    ASSERT_TRUE(box->layer()->hasCompositedLayerMapping());
 
     CompositedLayerMapping* compositedLayerMapping = box->layer()->compositedLayerMapping();
     ASSERT_TRUE(compositedLayerMapping->hasScrollingLayer());
     ASSERT(compositedLayerMapping->scrollingContentsLayer());
 
     GraphicsLayer* graphicsLayer = compositedLayerMapping->scrollingContentsLayer();
     ASSERT_EQ(box->layer()->scrollableArea(), graphicsLayer->scrollableArea());
 
     WebLayer* webScrollLayer = compositedLayerMapping->scrollingContentsLayer()->platformLayer();
     ASSERT_TRUE(webScrollLayer->scrollable());
@@ skipping 20 matching lines @@
     Element* overflowElement = m_webViewImpl->mainFrameImpl()->frame()->document()->getElementById("unscrollable-y");
     ASSERT(overflowElement);
 
     RenderObject* renderer = overflowElement->renderer();
     ASSERT_TRUE(renderer->isBox());
     ASSERT_TRUE(renderer->hasLayer());
 
     RenderBox* box = toRenderBox(renderer);
     ASSERT_TRUE(box->usesCompositedScrolling());
     ASSERT_EQ(PaintsIntoOwnBacking, box->layer()->compositingState());
+    ASSERT_TRUE(box->layer()->hasCompositedLayerMapping());
 
     CompositedLayerMapping* compositedLayerMapping = box->layer()->compositedLayerMapping();
     ASSERT_TRUE(compositedLayerMapping->hasScrollingLayer());
     ASSERT(compositedLayerMapping->scrollingContentsLayer());
 
     GraphicsLayer* graphicsLayer = compositedLayerMapping->scrollingContentsLayer();
     ASSERT_EQ(box->layer()->scrollableArea(), graphicsLayer->scrollableArea());
 
     WebLayer* webScrollLayer = compositedLayerMapping->scrollingContentsLayer()->platformLayer();
     ASSERT_TRUE(webScrollLayer->scrollable());
     ASSERT_TRUE(webScrollLayer->userScrollableHorizontal());
     ASSERT_FALSE(webScrollLayer->userScrollableVertical());
 
     overflowElement = m_webViewImpl->mainFrameImpl()->frame()->document()->getElementById("unscrollable-x");
     ASSERT(overflowElement);
 
     renderer = overflowElement->renderer();
     ASSERT_TRUE(renderer->isBox());
     ASSERT_TRUE(renderer->hasLayer());
 
     box = toRenderBox(renderer);
     ASSERT_TRUE(box->scrollableArea()->usesCompositedScrolling());
     ASSERT_EQ(PaintsIntoOwnBacking, box->layer()->compositingState());
+    ASSERT_TRUE(box->layer()->hasCompositedLayerMapping());
 
     compositedLayerMapping = box->layer()->compositedLayerMapping();
     ASSERT_TRUE(compositedLayerMapping->hasScrollingLayer());
     ASSERT(compositedLayerMapping->scrollingContentsLayer());
 
     graphicsLayer = compositedLayerMapping->scrollingContentsLayer();
     ASSERT_EQ(box->layer()->scrollableArea(), graphicsLayer->scrollableArea());
 
     webScrollLayer = compositedLayerMapping->scrollingContentsLayer()->platformLayer();
     ASSERT_TRUE(webScrollLayer->scrollable());
@@ skipping 88 matching lines @@
 TEST_F(ScrollingCoordinatorChromiumTest, setupScrollbarLayerShouldNotCrash)
 {
     registerMockedHttpURLLoad("setup_scrollbar_layer_crash.html");
     navigateTo(m_baseURL + "setup_scrollbar_layer_crash.html");
     forceFullCompositingUpdate();
     // This test document setup an iframe with scrollbars, then switch to
     // an empty document by javascript.
 }
 
 } // namespace