Make quoteCSSString an internal helper

Source/core/css/CSSMarkup.cpp

Index: Source/core/css/CSSMarkup.cpp
diff --git a/Source/core/css/CSSMarkup.cpp b/Source/core/css/CSSMarkup.cpp
index c5326afa96418b42b3f9dff642fbb05c7018365b..69764aa7de4ee7133cfc73a53fab16c7e1403bb3 100644
--- a/Source/core/css/CSSMarkup.cpp
+++ b/Source/core/css/CSSMarkup.cpp
@@ -159,7 +159,7 @@ static inline String quoteCSSStringInternal(const CharacterType* characters, uns
 }
 
 // We use single quotes for now because markup.cpp uses double quotes.
-String quoteCSSString(const String& string)
+static String quoteCSSString(const String& string)
 {
     // This function expands each character to at most 3 characters ('\u0010' -> '\' '1' '0') as well as adds
     // 2 quote characters (before and after). Make sure the resulting size (3 * length + 2) will not overflow unsigned.
@@ -248,4 +248,11 @@ void serializeString(const String& string, StringBuilder& appendTo)
     appendTo.append('\"');
 }
 
+String serializeString(const String& string)
+{
+    StringBuilder builder;
+    serializeString(string, builder);
+    return builder.toString();
+}
+
 } // namespace blink