Do not zero-initialize RawPtr.

Source/core/css/ElementRuleCollector.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 200 matching lines @@
         }
     }
     return result;
 }
 
 void ElementRuleCollector::appendCSSOMWrapperForRule(CSSStyleSheet* parentStyleSheet, StyleRule* rule)
 {
     // |parentStyleSheet| is 0 if and only if the |rule| is coming from User Agent. In this case,
     // it is safe to create CSSOM wrappers without parentStyleSheets as they will be used only
     // by inspector which will not try to edit them.
-    RefPtrWillBeRawPtr<CSSRule> cssRule;
+    RefPtrWillBeRawPtr<CSSRule> cssRule = nullptr;
     if (parentStyleSheet)
         cssRule = findStyleRule(parentStyleSheet, rule);
     else
         cssRule = rule->createCSSOMWrapper();
     ASSERT(!parentStyleSheet || cssRule);
     ensureRuleList()->rules().append(cssRule);
 }
 
 void ElementRuleCollector::sortAndTransferMatchedRules()
 {
@@ skipping 133 matching lines @@
     // information about "scope".
     int firstRuleIndex = -1, lastRuleIndex = -1;
     RuleRange ruleRange(firstRuleIndex, lastRuleIndex);
     // FIXME: Verify whether it's ok to ignore CascadeScope here.
     collectMatchingRules(MatchRequest(ruleSet), ruleRange, SelectorChecker::StaysWithinTreeScope);
 
     return m_matchedRules && !m_matchedRules->isEmpty();
 }
 
 } // namespace WebCore