Extracted UsbService as interface.

components/usb_service/usb_interface.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_USB_SERVICE_USB_INTERFACE_H_
 #define COMPONENTS_USB_SERVICE_USB_INTERFACE_H_
 
 #include "base/memory/ref_counted.h"
 #include "components/usb_service/usb_service_export.h"
 
@@ skipping 108 matching lines @@
 
   scoped_refptr<const UsbConfigDescriptor> config_;
   PlatformUsbInterface interface_;
 
   DISALLOW_COPY_AND_ASSIGN(UsbInterfaceDescriptor);
 };
 
 class USB_SERVICE_EXPORT UsbConfigDescriptor
     : public base::RefCounted<UsbConfigDescriptor> {
  public:
-  size_t GetNumInterfaces() const;
-  scoped_refptr<const UsbInterfaceDescriptor> GetInterface(size_t index) const;
+  virtual size_t GetNumInterfaces() const;
+  virtual scoped_refptr<const UsbInterfaceDescriptor> GetInterface(
+      size_t index) const;
+
+ protected:
+  // Constructor called in test only
+  UsbConfigDescriptor();
+  virtual ~UsbConfigDescriptor();
 
  private:
   friend class base::RefCounted<UsbConfigDescriptor>;
   friend class UsbDevice;
 
   explicit UsbConfigDescriptor(PlatformUsbConfigDescriptor config);
-  ~UsbConfigDescriptor();
 
   PlatformUsbConfigDescriptor config_;
 
   DISALLOW_COPY_AND_ASSIGN(UsbConfigDescriptor);
 };
 
 }  // namespace usb_service;
 
 #endif  // COMPONENTS_USB_SERVICE_USB_INTERFACE_H_