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

Source/core/rendering/RenderTableCell.h

Index: Source/core/rendering/RenderTableCell.h
diff --git a/Source/core/rendering/RenderTableCell.h b/Source/core/rendering/RenderTableCell.h
index 9a0da52dfc8e006867b7b2bab2f354d82011c45b..a938dac09a87032ec9d4e94ae950bf742ecb4388 100644
--- a/Source/core/rendering/RenderTableCell.h
+++ b/Source/core/rendering/RenderTableCell.h
@@ -99,7 +99,7 @@ public:
         int styleLogicalHeight = valueForLength(style()->logicalHeight(), 0, view());
         // In strict mode, box-sizing: content-box do the right thing and actually add in the border and padding.
         // Call computedCSSPadding* directly to avoid including implicitPadding.
-        if (!document()->inQuirksMode() && style()->boxSizing() != BORDER_BOX)
+        if (!document().inQuirksMode() && style()->boxSizing() != BORDER_BOX)
             styleLogicalHeight += (computedCSSPaddingBefore() + computedCSSPaddingAfter()).floor() + borderBefore() + borderAfter();
         return max(styleLogicalHeight, adjustedLogicalHeight);
     }