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

Source/core/css/CSSCursorImageValue.cpp

Index: Source/core/css/CSSCursorImageValue.cpp
diff --git a/Source/core/css/CSSCursorImageValue.cpp b/Source/core/css/CSSCursorImageValue.cpp
index dd68e0b98506299500eadc39d3813ef655a332aa..5b493a28fc648a62e9e580b570b598e41ce2847c 100644
--- a/Source/core/css/CSSCursorImageValue.cpp
+++ b/Source/core/css/CSSCursorImageValue.cpp
@@ -69,7 +69,7 @@ CSSCursorImageValue::~CSSCursorImageValue()
     for (; it != end; ++it) {
         SVGElement* referencedElement = *it;
         referencedElement->cursorImageValueRemoved();
-        if (SVGCursorElement* cursorElement = resourceReferencedByCursorElement(url, referencedElement->document()))
+        if (SVGCursorElement* cursorElement = resourceReferencedByCursorElement(url, &referencedElement->document()))
             cursorElement->removeClient(referencedElement);
     }
 }
@@ -96,7 +96,7 @@ bool CSSCursorImageValue::updateIfSVGCursorIsUsed(Element* element)
         return false;
 
     String url = toCSSImageValue(m_imageValue.get())->url();
-    if (SVGCursorElement* cursorElement = resourceReferencedByCursorElement(url, element->document())) {
+    if (SVGCursorElement* cursorElement = resourceReferencedByCursorElement(url, &element->document())) {
         // FIXME: This will override hot spot specified in CSS, which is probably incorrect.
         SVGLengthContext lengthContext(0);
         m_hasHotSpot = true;
@@ -106,7 +106,7 @@ bool CSSCursorImageValue::updateIfSVGCursorIsUsed(Element* element)
         float y = roundf(cursorElement->yCurrentValue().value(lengthContext));
         m_hotSpot.setY(static_cast<int>(y));
 
-        if (cachedImageURL() != element->document()->completeURL(cursorElement->hrefCurrentValue()))
+        if (cachedImageURL() != element->document().completeURL(cursorElement->hrefCurrentValue()))
             clearImageResource();
 
         SVGElement* svgElement = toSVGElement(element);