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

Source/core/html/RangeInputType.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 214 matching lines @@
     else
         return; // Did not match any key binding.
 
     newValue = stepRange.clampValue(newValue);
 
     if (newValue != current) {
         EventQueueScope scope;
         TextFieldEventBehavior eventBehavior = DispatchChangeEvent;
         setValueAsDecimal(newValue, eventBehavior, IGNORE_EXCEPTION);
 
-        if (AXObjectCache* cache = element()->document()->existingAXObjectCache())
+        if (AXObjectCache* cache = element()->document().existingAXObjectCache())
             cache->postNotification(element(), AXObjectCache::AXValueChanged, true);
         element()->dispatchFormControlChangeEvent();
     }
 
     event->setDefaultHandled();
 }
 
 void RangeInputType::createShadowSubtree()
 {
     ASSERT(element()->shadow());
 
-    Document* document = element()->document();
+    Document* document = &element()->document();
     RefPtr<HTMLDivElement> track = HTMLDivElement::create(document);
     track->setPart(AtomicString("-webkit-slider-runnable-track", AtomicString::ConstructFromLiteral));
     track->setAttribute(idAttr, ShadowElementNames::sliderTrack());
     track->appendChild(SliderThumbElement::create(document));
     RefPtr<HTMLElement> container = SliderContainerElement::create(document);
     container->appendChild(track.release());
     element()->userAgentShadowRoot()->appendChild(container.release());
 }
 
 RenderObject* RangeInputType::createRenderer(RenderStyle*) const
@@ skipping 129 matching lines @@
             right = middle;
     }
     const Decimal closestLeft = middle ? m_tickMarkValues[middle - 1] : Decimal::infinity(Decimal::Negative);
     const Decimal closestRight = middle != m_tickMarkValues.size() ? m_tickMarkValues[middle] : Decimal::infinity(Decimal::Positive);
     if (closestRight - value < value - closestLeft)
         return closestRight;
     return closestLeft;
 }
 
 } // namespace WebCore