Serialize <string> with double quotes

LayoutTests/fast/css/content-language-with-whitespace.html

Index: LayoutTests/fast/css/content-language-with-whitespace.html
diff --git a/LayoutTests/fast/css/content-language-with-whitespace.html b/LayoutTests/fast/css/content-language-with-whitespace.html
index ce893ee92aca261a06ae19eddfbc3ce56ab5c3bb..5f70efe7de699861b2300fb32d70f06f6d70063f 100644
--- a/LayoutTests/fast/css/content-language-with-whitespace.html
+++ b/LayoutTests/fast/css/content-language-with-whitespace.html
@@ -24,8 +24,8 @@ function languageOfNode(id) {
     var element = document.getElementById(id);
     return window.getComputedStyle(element).webkitLocale;
 }
-shouldBeEqualToString("languageOfNode('x')", "'ja_JP'");
-shouldBeEqualToString("languageOfNode('y')", "'ar'");
+shouldBeEqualToString("languageOfNode('x')", '"ja_JP"');
+shouldBeEqualToString("languageOfNode('y')", '"ar"');
 </script>
 </body>
 </html>