[Offline Prefetch] Send GeneratePageBundleRequest to the server

components/offline_pages/core/prefetch/proto/status.proto

+// Copyright 2017 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.
+
+syntax = "proto3";
+option optimize_for = LITE_RUNTIME;
+
+package offline_pages.proto;
+
+import "any.proto";
+
+enum Code {
+  OK = 0;
+  UNKNOWN = 2;
+  NOT_FOUND = 5;
+  FAILED_PRECONDITION = 9;
+}
+
+message Status {
+  // The status code.
+  int32 code = 1;
+
+  // A developer-facing error message, which should be in English.
+  string message = 2;
+
+  // A list of messages that carry the error details.  There will be a
+  // common set of message types for APIs to use.
+  repeated Any details = 3;
+}