Fix serialization of content property to always quote

LayoutTests/fast/css/lang-mapped-to-webkit-locale-dynamic.xhtml

Index: LayoutTests/fast/css/lang-mapped-to-webkit-locale-dynamic.xhtml
diff --git a/LayoutTests/fast/css/lang-mapped-to-webkit-locale-dynamic.xhtml b/LayoutTests/fast/css/lang-mapped-to-webkit-locale-dynamic.xhtml
index 3d89d9d8b8135773d4b74be9653c9d19a963a1f6..ac1d5a3920b27d348e95de868c8461153558a722 100644
--- a/LayoutTests/fast/css/lang-mapped-to-webkit-locale-dynamic.xhtml
+++ b/LayoutTests/fast/css/lang-mapped-to-webkit-locale-dynamic.xhtml
@@ -16,35 +16,35 @@ function runTest() {
     var x2 = document.getElementById("x2");
     var x3 = document.getElementById("x3");
 
-    shouldBeEqualToString("localeOfNode('x1')", "ko");
-    shouldBeEqualToString("localeOfNode('x2')", "ko");
-    shouldBeEqualToString("localeOfNode('x3')", "ar");
+    shouldBeEqualToString("localeOfNode('x1')", "'ko'");
+    shouldBeEqualToString("localeOfNode('x2')", "'ko'");
+    shouldBeEqualToString("localeOfNode('x3')", "'ar'");
 
     x1.lang = "ja";
-    shouldBeEqualToString("localeOfNode('x1')", "ja");
-    shouldBeEqualToString("localeOfNode('x2')", "ja");
-    shouldBeEqualToString("localeOfNode('x3')", "ar");
+    shouldBeEqualToString("localeOfNode('x1')", "'ja'");
+    shouldBeEqualToString("localeOfNode('x2')", "'ja'");
+    shouldBeEqualToString("localeOfNode('x3')", "'ar'");
 
     x3.lang = "";
     shouldBeEqualToString("localeOfNode('x3')", "auto");
 
     x3.removeAttribute("lang");
-    shouldBeEqualToString("localeOfNode('x3')", "ja");
+    shouldBeEqualToString("localeOfNode('x3')", "'ja'");
 
     // The "lang" attribute in the XML namespace should affect locale (since this is an XHTML document).
     var attr1 = document.createAttributeNS("http://www.w3.org/XML/1998/namespace", "xml:lang");
     attr1.value = "zh";
     x2.setAttributeNodeNS(attr1);
-    shouldBeEqualToString("localeOfNode('x2')", "zh");
+    shouldBeEqualToString("localeOfNode('x2')", "'zh'");
 
     x2.removeAttributeNode(attr1);
-    shouldBeEqualToString("localeOfNode('x2')", "ja");
+    shouldBeEqualToString("localeOfNode('x2')", "'ja'");
 
     // An attribute with local name "lang" not in the XML namespace should not affect locale.
     var attr2 = document.createAttributeNS("foobar", "fb:lang");
     attr2.value = "ph";
     x2.setAttributeNodeNS(attr2);
-    shouldBeEqualToString("localeOfNode('x2')", "ja");
+    shouldBeEqualToString("localeOfNode('x2')", "'ja'");
 
     // If we include js-test-post.js directly, the "TEST COMPLETE" output comes out of order.
     wasPostTestScriptParsed = true;