Add initial Controller to DownloadService

components/download/public/clients.h

 // 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.
 
 #ifndef COMPONENTS_DOWNLOAD_PUBLIC_CLIENTS_H_
 #define COMPONENTS_DOWNLOAD_PUBLIC_CLIENTS_H_
 
+#include <map>
+#include <memory>
+
+#include "components/download/public/client.h"
+
 namespace download {
 
 // A list of all clients that are able to make download requests through the
 // DownloadService.
 // To add a new client, update the metric DownloadService.DownloadClients in
 // histograms.xml and make sure to keep this list in sync.  Additions should be
 // treated as APPEND ONLY to make sure to keep both UMA metric semantics correct
 // but also to make sure the underlying database properly associates each
 // download with the right client.
 enum class DownloadClient {
   // Represents an uninitialized DownloadClient variable.
   INVALID = 0,
 
   // Test client values.  Meant to be used by the testing framework and not
   // production code.  Callers will be unable to access the DownloadService with
   // these test APIs.
   TEST = 1,
 
   OFFLINE_PAGE_PREFETCH = 2,
 
   BOUNDARY = 3,
 };
 
+using DownloadClientMap = std::map<DownloadClient, std::unique_ptr<Client>>;
+
 }  // namespace download
 
 #endif  // COMPONENTS_DOWNLOAD_PUBLIC_CLIENTS_H_