Add the "silent" property to the NotificationOptions dictionary.

Source/modules/notifications/ServiceWorkerRegistrationNotifications.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "modules/notifications/ServiceWorkerRegistrationNotifications.h"
 
 #include "bindings/core/v8/CallbackPromiseAdapter.h"
 #include "bindings/core/v8/ScriptPromiseResolver.h"
 #include "bindings/core/v8/V8ThrowException.h"
@@ skipping 28 matching lines @@
     // FIXME: Do the appropriate CORS checks on the icon URL.
 
     KURL iconUrl;
     if (options.hasIcon() && !options.icon().isEmpty()) {
         iconUrl = executionContext->completeURL(options.icon());
         if (!iconUrl.isValid())
             iconUrl = KURL();
     }
 
     WebNotificationData::Direction dir = options.dir() == "rtl" ? WebNotificationData::DirectionRightToLeft : WebNotificationData::DirectionLeftToRight;
-    WebNotificationData notification(title, dir, options.lang(), options.body(), options.tag(), iconUrl);
+    WebNotificationData notification(title, dir, options.lang(), options.body(), options.tag(), iconUrl, options.silent());
     WebNotificationShowCallbacks* callbacks = new CallbackPromiseAdapter<void, void>(resolver);
 
     SecurityOrigin* origin = executionContext->securityOrigin();
     ASSERT(origin);
 
     WebNotificationManager* notificationManager = Platform::current()->notificationManager();
     ASSERT(notificationManager);
 
     notificationManager->showPersistent(WebSerializedOrigin(*origin), notification, serviceWorkerRegistration.webRegistration(), callbacks);
     return promise;
 }
 
 } // namespace blink