Add WebUSB bindings and client interface [part 2]

public/platform/modules/webusb/WebUSBError.h

+// 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.
+
+#ifndef WebUSBError_h
+#define WebUSBError_h
+
+#include "public/platform/WebString.h"
+
+namespace blink {
+
+// Error object used to create DOMExceptions when a Web USB request cannot be
+// satisfied.
+struct WebUSBError {
+    enum class Error {
+        Device,
+        Security,
+        Service,
+        Transfer,
+    };
+
+    WebUSBError(Error error, const WebString& message)
+        : error(error)
+        , message(message)
+    {
+    }
+
+    Error error;
+    WebString message;
+};
+
+} // namespace blink
+
+#endif // WebUSBError_h