Oilpan: fix build after r197039.

Source/core/dom/StyleEngine.h

 /*
  * 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, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
@@ skipping 36 matching lines @@
 
 class CSSFontSelector;
 class CSSStyleSheet;
 class Node;
 class RuleFeatureSet;
 class ShadowTreeStyleSheetCollection;
 class StyleRuleFontFace;
 class StyleSheet;
 class StyleSheetContents;
 
-class CORE_EXPORT StyleEngine final : public CSSFontSelectorClient  {
+class CORE_EXPORT StyleEngine final : public NoBaseWillBeGarbageCollectedFinalized<StyleEngine>, public CSSFontSelectorClient  {
     WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED(StyleEngine);
+    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(StyleEngine);
 public:
 
     class IgnoringPendingStylesheet : public TemporaryChange<bool> {
     public:
         IgnoringPendingStylesheet(StyleEngine& engine)
             : TemporaryChange<bool>(engine.m_ignorePendingStylesheets, true)
         {
         }
     };
 
@@ skipping 186 matching lines @@
 
     RefPtrWillBeMember<CSSFontSelector> m_fontSelector;
 
     WillBeHeapHashMap<AtomicString, RawPtrWillBeMember<StyleSheetContents>> m_textToSheetCache;
     WillBeHeapHashMap<RawPtrWillBeMember<StyleSheetContents>, AtomicString> m_sheetToTextCache;
 };
 
 }
 
 #endif