Make sure <url>s are being serialized according to spec

LayoutTests/animations/interpolation/resources/interpolation-test.js

Index: LayoutTests/animations/interpolation/resources/interpolation-test.js
diff --git a/LayoutTests/animations/interpolation/resources/interpolation-test.js b/LayoutTests/animations/interpolation/resources/interpolation-test.js
index 19ce36406b93906c3528d22a15ab209181b53c3b..d0815d5c72cac9ff7f7bca94b3c902502db8d436 100644
--- a/LayoutTests/animations/interpolation/resources/interpolation-test.js
+++ b/LayoutTests/animations/interpolation/resources/interpolation-test.js
@@ -210,7 +210,7 @@
     var matches = value.match(/url\([^\)]*\)/g);
     if (matches !== null) {
       for (var i = 0; i < matches.length; ++i) {
-        var url = /url\(([^\)]*)\)/g.exec(matches[i])[1];
+        var url = /url\(\"([^\)]*)\)*\"/g.exec(matches[i])[1];
         anchor.href = url;
         anchor.pathname = '...' + anchor.pathname.substring(anchor.pathname.lastIndexOf('/'));
         value = value.replace(matches[i], 'url(' + anchor.href + ')');