Add support for disabling CSS Properties at runtime

Source/core/css/DOMWindowCSS.cpp

Index: Source/core/css/DOMWindowCSS.cpp
diff --git a/Source/core/css/DOMWindowCSS.cpp b/Source/core/css/DOMWindowCSS.cpp
index f9aa060c00211832fa5885a2559afb69517c744d..410f5c5b77d7b05835260a14fc959e8b6282e0da 100644
--- a/Source/core/css/DOMWindowCSS.cpp
+++ b/Source/core/css/DOMWindowCSS.cpp
@@ -31,6 +31,7 @@
 #include "DOMWindowCSS.h"
 
 #include "CSSParser.h"
+#include "core/page/RuntimeCSSEnabled.h"
 #include "StylePropertySet.h"
 #include <wtf/text/WTFString.h>
 
@@ -58,10 +59,12 @@ static String valueWithoutImportant(const String& value)
 bool DOMWindowCSS::supports(const String& property, const String& value) const
 {
     CSSPropertyID propertyID = cssPropertyID(property.stripWhiteSpace());
-
     if (propertyID == CSSPropertyInvalid)
         return false;
 
+    if (!RuntimeCSSEnabled::isCSSPropertyEnabled(propertyID))
+        return false;
+
     // CSSParser::parseValue() won't work correctly if !important is present,
     // so just get rid of it. It doesn't matter to supports() if it's actually
     // there or not, provided how it's specified in the value is correct.