Remove useless null checks from Node::document() call sites

Source/core/rendering/RenderTreeAsText.cpp

 /*
  * Copyright (C) 2004, 2006, 2007 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 786 matching lines @@
     if (behavior & RenderAsTextPrintingMode)
         printContext.begin(toRenderBox(renderer)->width());
 
     return externalRepresentation(toRenderBox(renderer), behavior);
 }
 
 String externalRepresentation(Element* element, RenderAsTextBehavior behavior)
 {
     // Doesn't support printing mode.
     ASSERT(!(behavior & RenderAsTextPrintingMode));
-    if (!(behavior & RenderAsTextDontUpdateLayout) && element->document())
+    if (!(behavior & RenderAsTextDontUpdateLayout))
         element->document()->updateLayout();
 
     RenderObject* renderer = element->renderer();
     if (!renderer || !renderer->isBox())
         return String();
 
     return externalRepresentation(toRenderBox(renderer), behavior | RenderAsTextShowAllLayers);
 }
 
 static void writeCounterValuesFromChildren(TextStream& stream, RenderObject* parent, bool& isFirstCounter)
@@ skipping 31 matching lines @@
     element->document()->updateLayout();
 
     RenderObject* renderer = element->renderer();
     if (!renderer || !renderer->isListItem())
         return String();
 
     return toRenderListItem(renderer)->markerText();
 }
 
 } // namespace WebCore