Add initial Controller to DownloadService

components/download/public/download_params.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_DOWNLOAD_PARAMS_H_
 #define COMPONENTS_DOWNLOAD_PUBLIC_DOWNLOAD_PARAMS_H_
 
 #include "base/callback.h"
 #include "base/time/time.h"
 #include "components/download/public/clients.h"
@@ skipping 84 matching lines @@
 // The |client| needs to be properly created and registered for this service for
 // the download to be accepted.
 struct DownloadParams {
   enum StartResult {
     // The download is accepted and persisted.
     ACCEPTED,
 
     // The DownloadService has too many downloads.  Backoff and retry.
     BACKOFF,
 
-    // Failed to create the download.  Invalid input parameters.
-    BAD_PARAMETERS,
+    // The DownloadService has no knowledge of the DownloadClient associated
+    // with this request.
+    UNEXPECTED_CLIENT,
+
+    // Failed to create the download.  The guid is already in use.
+    UNEXPECTED_GUID,
+
+    // The download was cancelled by the Client while it was being persisted.
+    CLIENT_CANCELLED,
+
+    // The DownloadService was unable to accept and persist this download due to
+    // an internal error like the underlying DB store failing to write to disk.
+    INTERNAL_ERROR,
 
     // TODO(dtrainor): Add more error codes.
   };
 
+  using StartCallback = base::Callback<void(const std::string&, StartResult)>;
+
   DownloadParams();
   DownloadParams(const DownloadParams& other);
   ~DownloadParams();
 
   // The feature that is requesting this download.
   DownloadClient client;
 
   // A unique GUID that represents this download.  See |base::GenerateGUID()|.
   std::string guid;
 
   // A callback that will be notified if this download has been accepted and
   // persisted by the DownloadService.
-  base::Callback<void(const DownloadParams&, StartResult)> callback;
+  StartCallback callback;
 
   // The parameters that determine under what device conditions this download
   // will occur.
   SchedulingParams scheduling_params;
 
   // The parameters that define the actual download request to make.
   RequestParams request_params;
 };
 
 }  // namespace download
 
 #endif  // COMPONENTS_DOWNLOAD_PUBLIC_DOWNLOAD_PARAMS_H_