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

Source/core/html/BaseButtonInputType.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) 2011 Apple 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.
@@ skipping 48 matching lines @@
     {
         return adoptRef(new NonSelectableText(document, data));
     }
 };
 
 // ----------------------------
 
 void BaseButtonInputType::createShadowSubtree()
 {
     ASSERT(element()->userAgentShadowRoot());
-    RefPtr<Text> text = NonSelectableText::create(element()->document(), element()->valueWithDefault());
+    RefPtr<Text> text = NonSelectableText::create(&element()->document(), element()->valueWithDefault());
     element()->userAgentShadowRoot()->appendChild(text);
 }
 
 void BaseButtonInputType::valueAttributeChanged()
 {
     toText(element()->userAgentShadowRoot()->firstChild())->setData(element()->valueWithDefault());
 }
 
 bool BaseButtonInputType::shouldSaveAndRestoreFormControlState() const
 {
@@ skipping 15 matching lines @@
 {
     return false;
 }
 
 void BaseButtonInputType::setValue(const String& sanitizedValue, bool, TextFieldEventBehavior)
 {
     element()->setAttribute(valueAttr, sanitizedValue);
 }
 
 } // namespace WebCore