Implement CSS.escape

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 b4548f3cfc50c34898acff32b542465732437a67..ccb50f294fd3d671407d98152c94601fa81d32b6 100644
--- a/Source/core/css/DOMWindowCSS.cpp
+++ b/Source/core/css/DOMWindowCSS.cpp
@@ -30,9 +30,13 @@
 #include "config.h"
 #include "core/css/DOMWindowCSS.h"
 
+#include "bindings/core/v8/ExceptionState.h"
+#include "core/css/CSSMarkup.h"
 #include "core/css/CSSPropertyMetadata.h"
 #include "core/css/StylePropertySet.h"
 #include "core/css/parser/CSSParser.h"
+#include "core/dom/ExceptionCode.h"
+#include "wtf/text/StringBuilder.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
@@ -54,4 +58,14 @@ bool DOMWindowCSS::supports(const String& conditionText)
     return CSSParser::parseSupportsCondition(conditionText);
 }
 
+String DOMWindowCSS::escape(const String& ident, ExceptionState& exceptionState)
+{
+    StringBuilder builder;
+    if (!serializeIdentifier(ident, builder)) {
+        exceptionState.throwDOMException(InvalidCharacterError, "The string contains an invalid character.");
+        return String();
+    }
+    return builder.toString();
+}
+
 }