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

mojo/spy/public/spy.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.
 
 module mojo.spy_api {
 
 enum Result {
   ALL_OK,
   INTERNAL_ERROR,
   INVALID_ID,
@@ skipping 12 matching lines @@
 enum ConnectionOptions {
   SKIP,
   PAUSE,
   RESUME,
   PEEK_MESSAGES
 };
 
 struct Message {
   uint32 id;
   uint32 time;
-  uint8[] data;
+  uint8[]? data;
 };
 
 [Client=SpyClient]
 interface SpyServer {
-  StartSession(Version version) => (Result result, string name);
+  StartSession(Version? version) => (Result result, string? name);
   StopSession() => (Result result);
   TrackConnection(uint32 id, ConnectionOptions options) => (Result result);
 };
 
 interface SpyClient {
   OnFatalError(Result result);
   OnSessionEnd(Result result);
-  OnClientConnection(string name, uint32 id, ConnectionOptions options);
-  OnMessage(Message message);
+  OnClientConnection(string? name, uint32 id, ConnectionOptions options);
+  OnMessage(Message? message);
 };
 
 }