Mojom: Blanket change to mark all pointer/handle fields as nullable.

mojo/services/public/interfaces/launcher/launcher.mojom

 // 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.
 
 import "mojo/services/public/interfaces/navigation/navigation.mojom"
 
 module mojo {
 
 interface Launcher {
   // Determines the correct handler application that can render a given URL.
   //
   // Sometimes this is known statically from the URL (e.g., from its scheme, or
   // because we already have an application locally that has said it can handle
   // the URL. Other times, we will actually fetch |url| to examine its
   // content-type and/or sniff it to determine the correct handler.
   //
   // When the caller receives the result, it should connect to the application
   // at |handler_url| and navigate it to |view_url|.
   //
   // Note: |view_url| might not be the same as |url|, e.g., in the case of
   // redirects. Applications should navigate to view_url, not |url| or
   // response->url.
   //
   // Note: |response| can be NULL in the case where a request was not needed to
   // determine the correct handler.
-  Launch(NavigationDetails details) =>
-      (string handler_url, string view_url, ResponseDetails response);
+  Launch(NavigationDetails? details) =>
+      (string? handler_url, string? view_url, ResponseDetails? response);
 };
 
 }