Have Node::document() return a reference instead of a pointer

Source/core/dom/shadow/InsertionPoint.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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 125 matching lines @@
         if (node->isInsertionPoint())
             return false;
 
         node = node->parentNode();
     }
     return true;
 }
 
 PassRefPtr<NodeList> InsertionPoint::getDistributedNodes()
 {
-    document()->updateDistributionForNodeIfNeeded(this);
+    document().updateDistributionForNodeIfNeeded(this);
 
     Vector<RefPtr<Node> > nodes;
     for (size_t i = 0; i < m_distribution.size(); ++i)
         nodes.append(m_distribution.at(i));
 
     return StaticNodeList::adopt(nodes);
 }
 
 bool InsertionPoint::rendererIsNeeded(const NodeRenderingContext& context)
 {
@@ skipping 124 matching lines @@
                 current = insertedTo;
                 results.append(insertedTo);
                 continue;
             }
         }
         return;
     }
 }
 
 } // namespace WebCore