Add the "silent" property to the NotificationOptions dictionary.

public/platform/modules/notifications/WebNotificationData.h

 // 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.
 
 #ifndef WebNotificationData_h
 #define WebNotificationData_h
 
 #include "public/platform/WebString.h"
 #include "public/platform/WebURL.h"
 
 namespace blink {
 
 // Structure representing the data associated with a Web Notification.
 struct WebNotificationData {
     enum Direction {
         DirectionLeftToRight,
         DirectionRightToLeft
     };
 
     WebNotificationData()
         : direction(DirectionLeftToRight)
+        , silent(false)
     {
     }
 
+    // FIXME: Remove this constructor when Chromium has switched to the new one.
     WebNotificationData(const WebString& title, Direction direction, const WebString& lang, const WebString& body, const WebString& tag, const WebURL& icon)
         : title(title)
         , direction(direction)
         , lang(lang)
         , body(body)
         , tag(tag)
         , icon(icon)
+        , silent(false)
     {
     }
 
+    WebNotificationData(const WebString& title, Direction direction, const WebString& lang, const WebString& body, const WebString& tag, const WebURL& icon, bool silent)
+        : title(title)
+        , direction(direction)
+        , lang(lang)
+        , body(body)
+        , tag(tag)
+        , icon(icon)
+        , silent(silent)
+    {
+    }
+
     WebString title;
     Direction direction;
     WebString lang;
     WebString body;
     WebString tag;
     WebURL icon;
+    bool silent;
 };
 
 } // namespace blink
 
 #endif // WebNotificationData_h