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

Source/bindings/v8/V8GCController.cpp

 /*
  * Copyright (C) 2009 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 57 matching lines @@
     }
 }
 
 Node* V8GCController::opaqueRootForGC(Node* node, v8::Isolate*)
 {
     // FIXME: Remove the special handling for image elements.
     // The same special handling is in V8GCController::gcTree().
     // Maybe should image elements be active DOM nodes?
     // See https://code.google.com/p/chromium/issues/detail?id=164882
     if (node->inDocument() || (node->hasTagName(HTMLNames::imgTag) && toHTMLImageElement(node)->hasPendingActivity()))
-        return node->document();
+        return &node->document();
 
     if (node->isAttributeNode()) {
         Node* ownerElement = toAttr(node)->ownerElement();
         if (!ownerElement)
             return node;
         node = ownerElement;
     }
 
     while (Node* parent = node->parentOrShadowHostNode())
         node = parent;
@@ skipping 325 matching lines @@
 {
     v8::HandleScope handleScope(isolate);
     v8::Local<v8::Context> context = v8::Context::New(isolate);
     if (context.IsEmpty())
         return;
     v8::Context::Scope contextScope(context);
     V8ScriptRunner::compileAndRunInternalScript(v8String("if (gc) gc();", isolate), isolate);
 }
 
 }  // namespace WebCore