ServiceWorker: Update IDLs to use ScalarValueString

Source/modules/serviceworkers/ServiceWorker.idl

Index: Source/modules/serviceworkers/ServiceWorker.idl
diff --git a/Source/modules/serviceworkers/ServiceWorker.idl b/Source/modules/serviceworkers/ServiceWorker.idl
index e1033e4840bb2d0ecfd49bddb2d93c6bf055a13b..b9a2bddfd239b3c3b760f0fed680d50d03efde2e 100644
--- a/Source/modules/serviceworkers/ServiceWorker.idl
+++ b/Source/modules/serviceworkers/ServiceWorker.idl
@@ -27,6 +27,8 @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
+
+// https://slightlyoff.github.io/ServiceWorker/spec/service_worker/index.html#service-worker-interface
 [
     ActiveDOMObject,
     RuntimeEnabled=ServiceWorker
@@ -35,8 +37,9 @@
     // FIXME: Should inherit this from Worker.
     [Custom, RaisesException] void postMessage(SerializedScriptValue message, optional MessagePort[] messagePorts);
 
-    readonly attribute DOMString scope;
-    readonly attribute DOMString url;
+    readonly attribute ScalarValueString scope;
+    readonly attribute ScalarValueString url;
+    // FIXME: Should be ServiceWorkerState enum, not DOMString.
     readonly attribute DOMString state;
     attribute EventHandler onstatechange;
 };