webusb: Reject the promise if the device is already open.

third_party/WebKit/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 {
+        InvalidState,
         Network,
         NotFound,
         Security,
     };
 
     WebUSBError(Error error, const WebString& message)
         : error(error)
         , message(message)
     {
     }
 
     Error error;
     WebString message;
 };
 
 } // namespace blink
 
 #endif // WebUSBError_h