Use Mojo enum types in the C++ USB interface

device/usb/public/interfaces/device.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 device.mojom;
 
 enum UsbOpenDeviceError {
   // Opening the device succeeded.
   OK,
 
   // The operating system denied access to the device.
   ACCESS_DENIED,
 
   // The device is already open.
   ALREADY_OPEN,
 };
 
 enum UsbTransferDirection {
-  INBOUND,
+  INBOUND = 0,
   OUTBOUND,
 };
 
 enum UsbControlTransferType {
   STANDARD,
   CLASS,
   VENDOR,
   RESERVED
 };
 
 enum UsbControlTransferRecipient {

[mcasas, 2017/04/17 17:15:15]

nit: This seems pretty similar to the Spec's "USBRecipient" enum,
perhaps we could add a link such as, e.g. [1] ? (Similarly
for USBRequestType <-> Spec's UsbControlTransferType).

[1] https://wicg.github.io/webusb/#enumdef-usbrecipient

[Reilly Grant (use Gerrit), 2017/04/17 19:20:48]

Done.

   DEVICE,
   INTERFACE,
   ENDPOINT,
   OTHER
 };
 
-enum UsbEndpointType {
+enum UsbTransferType {
+  CONTROL = 0,
+  ISOCHRONOUS,
   BULK,
   INTERRUPT,
-  ISOCHRONOUS,
 };
 
 struct UsbEndpointInfo {
   uint8 endpoint_number;
   UsbTransferDirection direction;
-  UsbEndpointType type;
+  UsbTransferType type;
   uint32 packet_size;
 };
 
 struct UsbAlternateInterfaceInfo {
   uint8 alternate_setting;
   uint8 class_code;
   uint8 subclass_code;
   uint8 protocol_code;
   string? interface_name;
   array<UsbEndpointInfo> endpoints;
@@ skipping 31 matching lines @@
 };
 
 struct UsbControlTransferParams {
   UsbControlTransferType type;
   UsbControlTransferRecipient recipient;
   uint8 request;
   uint16 value;
   uint16 index;
 };
 
+// This enum is exposed through the chrome.usb extension API so existing values
+// should not be changed or reordered.
 enum UsbTransferStatus {
   // The transfer completed successfully.
-  COMPLETED,
+  COMPLETED = 0,
 
   // The transfer failed due to a non-specific error.
   TRANSFER_ERROR,
 
-  // The transfer was not allowed.
-  PERMISSION_DENIED,
-
   // The transfer timed out.
   TIMEOUT,
 
   // The transfer was cancelled.
   CANCELLED,
 
   // The transfer stalled.
   STALLED,
 
   // The transfer failed because the device was disconnected from the host.
   DISCONNECT,
 
   // The transfer succeeded, but the device sent more data than was requested.
   // This applies only to inbound transfers.
   BABBLE,
 
   // The transfer succeeded, but the device sent less data than was requested.
   // This applies only to inbound transfers.
   SHORT_PACKET,
+
+  // The transfer was not allowed.
+  PERMISSION_DENIED,
 };
 
 struct UsbIsochronousPacket {
   uint32 length;
   uint32 transferred_length;
   UsbTransferStatus status;
 };
 
 interface UsbDevice {
   // Opens the device. Methods below require the device be opened first.
@@ skipping 120 matching lines @@
   // indicates no timeout: the request will remain pending indefinitely until
   // completed or otherwise terminated.
 
   // |packets| contains the status of each packet sent to the device, in order.
   IsochronousTransferOut(uint8 endpoint_number,
                          array<uint8> data,
                          array<uint32> packet_lengths,
                          uint32 timeout)
       => (array<UsbIsochronousPacket> packets);
 };