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

Source/core/html/LinkImport.cpp

 /*
  * Copyright (C) 2013 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 49 matching lines @@
         return 0;
     return m_loader->importedDocument();
 }
 
 void LinkImport::process()
 {
     if (m_loader)
         return;
     if (!m_owner)
         return;
-    if (!m_owner->document()->frame() && !m_owner->document()->import())
+    if (!m_owner->document().frame() && !m_owner->document().import())
         return;
 
-    if (!m_owner->document()->import()) {
-        ASSERT(m_owner->document()->frame()); // The document should be the master.
-        HTMLImportsController::provideTo(m_owner->document());
+    if (!m_owner->document().import()) {
+        ASSERT(m_owner->document().frame()); // The document should be the master.
+        HTMLImportsController::provideTo(&m_owner->document());
     }
 
     LinkRequestBuilder builder(m_owner);
     if (!builder.isValid()) {
         didFinish();
         return;
     }
 
-    HTMLImport* parent = m_owner->document()->import();
+    HTMLImport* parent = m_owner->document().import();
     HTMLImportsController* controller = parent->controller();
     m_loader = controller->createLoader(parent, builder.build(true));
     if (!m_loader) {
         didFinish();
         return;
     }
 
     m_loader->addClient(this);
 }
 
@@ skipping 18 matching lines @@
         return;
     m_owner->scheduleEvent();
 }
 
 bool LinkImport::hasLoaded() const
 {
     return m_loader && m_loader->isLoaded();
 }
 
 } // namespace WebCore