Add a generated ComputedStyleBase class that ComputedStyle extends

third_party/WebKit/Source/core/style/ComputedStyleConstants.h

Index: third_party/WebKit/Source/core/style/ComputedStyleConstants.h
diff --git a/third_party/WebKit/Source/core/style/ComputedStyleConstants.h b/third_party/WebKit/Source/core/style/ComputedStyleConstants.h
index fcad1d6fc00fa93beb1e3783e4c86043ef721f5a..3e2f262e84236550dc31b7b9ec04028de78cfe02 100644
--- a/third_party/WebKit/Source/core/style/ComputedStyleConstants.h
+++ b/third_party/WebKit/Source/core/style/ComputedStyleConstants.h
@@ -26,6 +26,7 @@
 #ifndef ComputedStyleConstants_h
 #define ComputedStyleConstants_h
 
+#include "core/BaseComputedStyleConstants.h"
 #include <cstddef>
 
 namespace blink {
@@ -386,8 +387,6 @@ enum ECaptionSide {
 
 enum EListStylePosition { ListStylePositionOutside, ListStylePositionInside };
 
-enum class EVisibility { Visible, Hidden, Collapse };
-
 enum ECursor {
     // The following must match the order in CSSValueKeywords.in.
     CURSOR_AUTO,