Don't include ComputedStyle.h where not needed.

third_party/WebKit/Source/core/html/HTMLOptGroupElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2010 Apple Inc. All rights
  * reserved.
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 15 matching lines @@
 #include "core/html/HTMLOptGroupElement.h"
 
 #include "core/HTMLNames.h"
 #include "core/dom/NodeComputedStyle.h"
 #include "core/dom/Text.h"
 #include "core/editing/EditingUtilities.h"
 #include "core/html/HTMLContentElement.h"
 #include "core/html/HTMLDivElement.h"
 #include "core/html/HTMLSelectElement.h"
 #include "core/html/shadow/ShadowElementNames.h"
+#include "core/style/ComputedStyle.h"
 #include "wtf/StdLibExtras.h"
 #include "wtf/text/CharacterNames.h"
 
 namespace blink {
 
 using namespace HTMLNames;
 
 inline HTMLOptGroupElement::HTMLOptGroupElement(Document& document)
     : HTMLElement(optgroupTag, document) {
   setHasCustomStyleCallbacks();
 }
 
+// An explicit empty destructor should be in HTMLOptGroupElement.cpp, because
+// if an implicit destructor is used or an empty destructor is defined in
+// HTMLOptGroupElement.h, when including HTMLOptGroupElement.h,
+// msvc tries to expand the destructor and causes
+// a compile error because of lack of ComputedStyle definition.
+HTMLOptGroupElement::~HTMLOptGroupElement() {}
+
 HTMLOptGroupElement* HTMLOptGroupElement::create(Document& document) {
   HTMLOptGroupElement* optGroupElement = new HTMLOptGroupElement(document);
   optGroupElement->ensureUserAgentShadowRoot();
   return optGroupElement;
 }
 
 bool HTMLOptGroupElement::isDisabledFormControl() const {
   return fastHasAttribute(disabledAttr);
 }
 
@@ skipping 121 matching lines @@
   label.setTextContent(labelText);
   label.setAttribute(aria_labelAttr, AtomicString(labelText));
 }
 
 HTMLDivElement& HTMLOptGroupElement::optGroupLabelElement() const {
   return *toHTMLDivElementOrDie(userAgentShadowRoot()->getElementById(
       ShadowElementNames::optGroupLabel()));
 }
 
 }  // namespace blink