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

Source/core/css/SelectorChecker.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
@@ skipping 135 matching lines @@
             if (!matchesCustomPseudoElement(context.element, context.selector))
                 return SelectorFailsLocally;
         } else if (context.selector->isContentPseudoElement()) {
             if (!context.element->isInShadowTree() || !context.element->isInsertionPoint())
                 return SelectorFailsLocally;
         } else {
             if ((!context.elementStyle && m_mode == ResolvingStyle) || m_mode == QueryingRules)
                 return SelectorFailsLocally;
 
             PseudoId pseudoId = CSSSelector::pseudoId(context.selector->pseudoType());
-            if (pseudoId == FIRST_LETTER) {
-                if (Document* document = context.element->document())
-                    document->styleSheetCollections()->setUsesFirstLetterRules(true);
-            }
+            if (pseudoId == FIRST_LETTER)
+                context.element->document()->styleSheetCollections()->setUsesFirstLetterRules(true);
             if (pseudoId != NOPSEUDO && m_mode != SharingRules)
                 dynamicPseudo = pseudoId;
         }
     }
 
     // The rest of the selectors has to match
     CSSSelector::Relation relation = context.selector->relation();
 
     // Prepare next selector
     const CSSSelector* historySelector = context.selector->tagHistory();
@@ skipping 498 matching lines @@
                 }
                 if (element->active() || InspectorInstrumentation::forcePseudoState(element, CSSSelector::PseudoActive))
                     return true;
             }
             break;
         case CSSSelector::PseudoEnabled:
             if (element && (element->isFormControlElement() || element->hasTagName(optionTag) || isHTMLOptGroupElement(element)))
                 return !element->isDisabledFormControl();
             break;
         case CSSSelector::PseudoFullPageMedia:
-            return element && element->document() && element->document()->isMediaDocument();
+            return element && element->document()->isMediaDocument();
             break;
         case CSSSelector::PseudoDefault:
             return element && element->isDefaultButtonForForm();
         case CSSSelector::PseudoDisabled:
             if (element && (element->isFormControlElement() || element->hasTagName(optionTag) || isHTMLOptGroupElement(element)))
                 return element->isDisabledFormControl();
             break;
         case CSSSelector::PseudoReadOnly:
             return element && element->matchesReadOnlyPseudoClass();
         case CSSSelector::PseudoReadWrite:
@@ skipping 305 matching lines @@
     return element->focused() && isFrameFocused(element);
 }
 
 template
 SelectorChecker::Match SelectorChecker::match(const SelectorCheckingContext&, PseudoId&, const DOMSiblingTraversalStrategy&) const;
 
 template
 SelectorChecker::Match SelectorChecker::match(const SelectorCheckingContext&, PseudoId&, const ShadowDOMSiblingTraversalStrategy&) const;
 
 }