Don't include ComputedStyle.h where not needed.

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

Index: third_party/WebKit/Source/core/html/HTMLOptGroupElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLOptGroupElement.cpp b/third_party/WebKit/Source/core/html/HTMLOptGroupElement.cpp
index d0bf597f41a5725b68521c02ba9abef9fdea39da..0feeb29edce19a1c95e236a12c237c7be81b00bb 100644
--- a/third_party/WebKit/Source/core/html/HTMLOptGroupElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLOptGroupElement.cpp
@@ -33,6 +33,7 @@
 #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"
 
@@ -45,6 +46,13 @@ inline HTMLOptGroupElement::HTMLOptGroupElement(Document& 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();