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 0fc4d2e3dcb9f89fe2dc28fecdafa64e7b5e905f..40b1984d625c0d465d70d98e34e91d215f6f00c9 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/ComputedStyleBaseConstants.h"
 #include <cstddef>
 
 namespace blink {
@@ -403,10 +404,6 @@ enum ECaptionSide {
 
 enum EListStylePosition { ListStylePositionOutside, ListStylePositionInside };
 
-// TODO(sashab): Add a static_assert when this is used in bitfields to ensure it
-// uses unsigned as the underlying type.
-enum class EVisibility : unsigned { Visible, Hidden, Collapse };
-
 enum ECursor {
     // The following must match the order in CSSValueKeywords.in.
     CURSOR_AUTO,