Make struct members nullable so demo_launcher no longer crashes.

mojo/services/public/interfaces/network/url_loader.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/network/network_error.mojom"
 
 module mojo {
 
 struct URLRequest {
   // The URL to load.
   string url;
 
   // The HTTP method if applicable.
   string method = "GET";
 
   // Additional HTTP request headers.
-  string[] headers;
+  string[]? headers;
 
   // The payload for the request body, represented as a concatenation of data
   // streams. For HTTP requests, the method must be set to "POST" or "PUT".
-  handle<data_pipe_consumer>[] body;
+  handle<data_pipe_consumer>[]? body;
 
   // The number of bytes to be read from |body|. A Content-Length header of
   // this value will be sent. Set to -1 if length is unknown, which will cause
   // |body| to be uploaded using a chunked encoding.
   int64 body_length = 0;
 
   // The buffer size of the data pipe returned in URLResponse's |body| member.
   // A value of 0 indicates that the default buffer size should be used.  This
   // value is just a suggestion. The URLLoader may choose to ignore this value.
   uint32 response_body_buffer_size = 0;
 
   // If set to true, then redirects will be automatically followed. Otherwise,
   // when a redirect is encounterd, FollowRedirect must be called to proceed.
   bool auto_follow_redirects = false;
 
   // If set to true, then the HTTP request will bypass the local cache and will
   // have a 'Cache-Control: nocache' header added in that causes any proxy
   // servers to also not satisfy the request from their cache.  This has the
   // effect of forcing a full end-to-end fetch.
   bool bypass_cache = false;
 };
 
 struct URLResponse {
   // If the response resulted in a network level error, this field will be set.
-  NetworkError error;
+  NetworkError? error;
 
   // The response body stream. Read from this data pipe to receive the bytes of
   // response body.
   handle<data_pipe_consumer> body;
 
   // The final URL of the response, after redirects have been followed.
   string url;
 
   // The HTTP status code. 0 if not applicable.
   uint32 status_code;
 
   // The HTTP status line.
   string status_line;
 
   // The HTTP response headers.
   string[] headers;
 
   // The MIME type of the response body.
   string mime_type;
 
   // The character set of the response body.
   string charset;
 
   // These fields are set to non-NULL if this response corresponds to a
   // redirect.  Call the |FollowRedirect| method on the URLLoader instance to
   // follow this redirect.
-  string redirect_method;
-  string redirect_url;
+  string? redirect_method;
+  string? redirect_url;
 };
 
 struct URLLoaderStatus {
   // If the loader has failed due to a network level error, this field will be
   // set.
-  NetworkError error;
+  NetworkError? error;
 
   // Set to true if the URLLoader is still working. Set to false once an error
   // is encountered or the response body is completely copied to the response
   // body stream.
   bool is_loading;
 
   // TODO(darin): Add further details about the stages of loading (e.g.,
   // "resolving host") that happen prior to receiving bytes.
 };
 
 interface URLLoader {
   // Loads the given |request|, asynchronously producing |response|. Consult
   // |response| to determine if the request resulted in an error, was
   // redirected, or has a response body to be consumed.
   Start(URLRequest request) => (URLResponse response);
 
   // If the request passed to |Start| had |auto_follow_redirects| set to false,
   // then upon receiving an URLResponse with a non-NULL |redirect_url| field,
   // |FollowRedirect| may be called to load the URL indicated by the redirect.
   FollowRedirect() => (URLResponse response);
 
   // Query status about the URLLoader.
   QueryStatus() => (URLLoaderStatus status);
 };
 
 }