Add getConfiguration method to USBDevice.

Source/modules/webusb/USBConfiguration.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 USBConfiguration_h
 #define USBConfiguration_h
 
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "platform/heap/Handle.h"
 #include "public/platform/modules/webusb/WebUSBDeviceInfo.h"
 
 namespace blink {
 
 class ExceptionState;
 class USBDevice;
 class USBInterface;
 
 class USBConfiguration
     : public GarbageCollected<USBConfiguration>
     , public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
     static USBConfiguration* create(const USBDevice*, size_t configurationIndex);
     static USBConfiguration* create(const USBDevice*, size_t configurationValue, ExceptionState&);
+    static USBConfiguration* createFromValue(const USBDevice*, uint8_t configurationValue);
 
     USBConfiguration(const USBDevice*, size_t configurationIndex);
 
     const WebUSBDeviceInfo::Configuration& info() const;
 
     uint8_t configurationValue() const;
     String configurationName() const;
     HeapVector<Member<USBInterface>> interfaces() const;
 
     DECLARE_TRACE();
 
 private:
     Member<const USBDevice> m_device;
     const size_t m_configurationIndex;
 };
 
 } // namespace blink
 
 #endif // USBConfiguration_h