Do not zero-initialize RawPtr.

Source/core/dom/StyleEngine.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 561 matching lines @@
     // It is not the original sheet anymore.
     if (contents.isMutable())
         return false;
     if (!contents.hasSyntacticallyValidCSSHeader())
         return false;
     return true;
 }
 
 PassRefPtrWillBeRawPtr<CSSStyleSheet> StyleEngine::createSheet(Element* e, const String& text, TextPosition startPosition, bool createdByParser)
 {
-    RefPtrWillBeRawPtr<CSSStyleSheet> styleSheet;
+    RefPtrWillBeRawPtr<CSSStyleSheet> styleSheet = nullptr;
 
     e->document().styleEngine()->addPendingSheet();
 
     if (!e->document().inQuirksMode()) {
         AtomicString textContent(text);
 
         HashMap<AtomicString, StyleSheetContents*>::AddResult result = m_textToSheetCache.add(textContent, 0);
         if (result.isNewEntry || !result.storedValue->value) {
             styleSheet = StyleEngine::parseSheet(e, text, startPosition, createdByParser);
             if (result.isNewEntry && isCacheableForStyleElement(*styleSheet->contents())) {
@@ skipping 12 matching lines @@
         styleSheet = StyleEngine::parseSheet(e, text, startPosition, createdByParser);
     }
 
     ASSERT(styleSheet);
     styleSheet->setTitle(e->title());
     return styleSheet;
 }
 
 PassRefPtrWillBeRawPtr<CSSStyleSheet> StyleEngine::parseSheet(Element* e, const String& text, TextPosition startPosition, bool createdByParser)
 {
-    RefPtrWillBeRawPtr<CSSStyleSheet> styleSheet;
+    RefPtrWillBeRawPtr<CSSStyleSheet> styleSheet = nullptr;
     styleSheet = CSSStyleSheet::createInline(e, KURL(), startPosition, e->document().inputEncoding());
     styleSheet->contents()->parseStringAtPosition(text, startPosition, createdByParser);
     return styleSheet;
 }
 
 void StyleEngine::removeSheet(StyleSheetContents* contents)
 {
     HashMap<StyleSheetContents*, AtomicString>::iterator it = m_sheetToTextCache.find(contents);
     if (it == m_sheetToTextCache.end())
         return;
 
     m_textToSheetCache.remove(it->value);
     m_sheetToTextCache.remove(contents);
 }
 
 void StyleEngine::trace(Visitor* visitor)
 {
     visitor->trace(m_injectedAuthorStyleSheets);
     visitor->trace(m_authorStyleSheets);
     visitor->trace(m_documentStyleSheetCollection);
     visitor->trace(m_styleSheetCollectionMap);
 }
 
 }