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

Source/core/html/HTMLImageElement.cpp

Index: Source/core/html/HTMLImageElement.cpp
diff --git a/Source/core/html/HTMLImageElement.cpp b/Source/core/html/HTMLImageElement.cpp
index 4b96259134ed6cf79299a7733478d6f69e015d23..bf88109ed9ecad7b640245f02d5216edaa77a176 100644
--- a/Source/core/html/HTMLImageElement.cpp
+++ b/Source/core/html/HTMLImageElement.cpp
@@ -222,9 +222,9 @@ int HTMLImageElement::width(bool ignorePendingStylesheets)
     }
 
     if (ignorePendingStylesheets)
-        document()->updateLayoutIgnorePendingStylesheets();
+        document().updateLayoutIgnorePendingStylesheets();
     else
-        document()->updateLayout();
+        document().updateLayout();
 
     RenderBox* box = renderBox();
     return box ? adjustForAbsoluteZoom(box->contentBoxRect().pixelSnappedWidth(), box) : 0;
@@ -245,9 +245,9 @@ int HTMLImageElement::height(bool ignorePendingStylesheets)
     }
 
     if (ignorePendingStylesheets)
-        document()->updateLayoutIgnorePendingStylesheets();
+        document().updateLayoutIgnorePendingStylesheets();
     else
-        document()->updateLayout();
+        document().updateLayout();
 
     RenderBox* box = renderBox();
     return box ? adjustForAbsoluteZoom(box->contentBoxRect().pixelSnappedHeight(), box) : 0;
@@ -296,7 +296,7 @@ void HTMLImageElement::setHeight(int value)
 
 KURL HTMLImageElement::src() const
 {
-    return document()->completeURL(getAttribute(srcAttr));
+    return document().completeURL(getAttribute(srcAttr));
 }
 
 void HTMLImageElement::setSrc(const String& value)
@@ -342,7 +342,7 @@ void HTMLImageElement::addSubresourceAttributeURLs(ListHashSet<KURL>& urls) cons
 
     addSubresourceURL(urls, src());
     // FIXME: What about when the usemap attribute begins with "#"?
-    addSubresourceURL(urls, document()->completeURL(getAttribute(usemapAttr)));
+    addSubresourceURL(urls, document().completeURL(getAttribute(usemapAttr)));
 }
 
 void HTMLImageElement::didMoveToNewDocument(Document* oldDocument)
@@ -362,7 +362,7 @@ bool HTMLImageElement::isServerMap() const
     if (usemap.string()[0] == '#')
         return false;
 
-    return document()->completeURL(stripLeadingAndTrailingHTMLSpaces(usemap)).isEmpty();
+    return document().completeURL(stripLeadingAndTrailingHTMLSpaces(usemap)).isEmpty();
 }
 
 Image* HTMLImageElement::imageContents()