Provide a mechanism for the GCM driver to send message receipts to GCM.

components/gcm_driver/gcm_message_status.h

+// 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.
+
+#ifndef COMPONENTS_GCM_DRIVER_GCM_MESSAGE_STATUS_H_
+#define COMPONENTS_GCM_DRIVER_GCM_MESSAGE_STATUS_H_
+
+namespace gcm {
+
+// Enumeration to be used for describing the status of a GCM message.
+enum GCMMessageStatus {

[Peter Beverloo, 2017/01/13 01:46:12]

Can this be an "enum class"? That would allow us to forward declare it in the
other header files, allowing this file only to be included where it's actually
needed.

[harkness, 2017/01/19 13:20:42]

Done.

+  // 0 reserved for unresolved.
+  GCM_UNRESOLVED = 0,
+  // 1 reserved for success.
+  GCM_SUCCESS = 1,
+
+  // 2 - 99 reserved for the GCM communication error types.
+  GCM_INVALID_SUBTYPE = 2,
+  GCM_ENCRYPTION_FAILURE = 3,
+  GCM_UNKNOWN_MESSAGE_TYPE = 4,
+  GCM_NO_APP_HANDLER = 5,
+  GCM_INVALID_MESSAGE_TAG = 6,
+};
+
+}  // namespace gcm
+
+#endif  // COMPONENTS_GCM_DRIVER_GCM_MESSAGE_STATUS_H_