Do not zero-initialize RawPtr.

Source/core/css/StyleRule.cpp

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * (C) 2002-2003 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2002, 2005, 2006, 2008, 2012 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 186 matching lines @@
     case Keyframe:
         ASSERT_NOT_REACHED();
         return nullptr;
     }
     ASSERT_NOT_REACHED();
     return nullptr;
 }
 
 PassRefPtrWillBeRawPtr<CSSRule> StyleRuleBase::createCSSOMWrapper(CSSStyleSheet* parentSheet, CSSRule* parentRule) const
 {
-    RefPtrWillBeRawPtr<CSSRule> rule;
+    RefPtrWillBeRawPtr<CSSRule> rule = nullptr;
     StyleRuleBase* self = const_cast<StyleRuleBase*>(this);
     switch (type()) {
     case Style:
         rule = CSSStyleRule::create(toStyleRule(self), parentSheet);
         break;
     case Page:
         rule = CSSPageRule::create(toStyleRulePage(self), parentSheet);
         break;
     case FontFace:
         rule = CSSFontFaceRule::create(toStyleRuleFontFace(self), parentSheet);
@@ skipping 228 matching lines @@
         m_properties = m_properties->mutableCopy();
     return *toMutableStylePropertySet(m_properties);
 }
 
 void StyleRuleFilter::setProperties(PassRefPtr<StylePropertySet> properties)
 {
     m_properties = properties;
 }
 
 } // namespace WebCore