Move mojom definitions of URL{Request,Response} into SDK

mojo/public/interfaces/network/url_request.mojom

+// Copyright 2015 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;
+
+struct URLRequest {
+  // The URL to load.
+  string url;
+
+  // The HTTP method if applicable.
+  string method = "GET";
+
+  // Additional HTTP request headers.
+  array<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".
+  array<handle<data_pipe_consumer>>? body;
+
+  // 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;
+
+  // The referrer request header.
+  string? referrer;
+};