Detect if webkitNotifications is available and remove webkit prefix (replaced

sdk/lib/html/dartium/html_dartium.dart

Index: sdk/lib/html/dartium/html_dartium.dart
diff --git a/sdk/lib/html/dartium/html_dartium.dart b/sdk/lib/html/dartium/html_dartium.dart
index 8b45becf1816591139c73d7145c0387667b14187..ce209c457387adddac1a6e06b08cea32c84f440f 100644
--- a/sdk/lib/html/dartium/html_dartium.dart
+++ b/sdk/lib/html/dartium/html_dartium.dart
@@ -18648,9 +18648,15 @@ class NotificationEvents extends Events {
 
 
 /// @domName NotificationCenter
+@SupportedBrowser(SupportedBrowser.CHROME)
+@SupportedBrowser(SupportedBrowser.SAFARI)
+@Experimental()
 class NotificationCenter extends NativeFieldWrapperClass1 {
   NotificationCenter.internal();
 
+  /// Checks if this type is supported on the current platform.
+  static bool get supported => true;
+
 
   /** @domName NotificationCenter.checkPermission */
   int checkPermission() native "NotificationCenter_checkPermission_Callback";
@@ -27009,7 +27015,10 @@ class Window extends EventTarget implements WindowBase {
 
 
   /** @domName DOMWindow.webkitNotifications */
-  NotificationCenter get webkitNotifications native "DOMWindow_webkitNotifications_Getter";
+  @SupportedBrowser(SupportedBrowser.CHROME)
+  @SupportedBrowser(SupportedBrowser.SAFARI)
+  @Experimental()
+  NotificationCenter get notifications native "DOMWindow_webkitNotifications_Getter";
 
 
   /** @domName DOMWindow.webkitStorageInfo */