Add device path enumeration to the new Windows USB backend.

device/usb/usb_device.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 DEVICE_USB_USB_DEVICE_H_
 #define DEVICE_USB_USB_DEVICE_H_
 
 #include <stdint.h>
 
 #include <list>
@@ skipping 78 matching lines @@
 
   // Creates a UsbDeviceHandle for further manipulation.
   virtual void Open(const OpenCallback& callback) = 0;
 
   void AddObserver(Observer* observer);
   void RemoveObserver(Observer* observer);
 
  protected:
   friend class UsbService;
 
+  UsbDevice();
   UsbDevice(const UsbDeviceDescriptor& descriptor,
             const base::string16& manufacturer_string,
             const base::string16& product_string,
             const base::string16& serial_number);
   UsbDevice(uint16_t usb_version,
             uint8_t device_class,
             uint8_t device_subclass,
             uint8_t device_protocol,
             uint16_t vendor_id,
             uint16_t product_id,
@@ skipping 18 matching lines @@
   std::unique_ptr<WebUsbAllowedOrigins> webusb_allowed_origins_;
   GURL webusb_landing_page_;
 
  private:
   friend class base::RefCountedThreadSafe<UsbDevice>;
   friend class UsbDeviceHandleImpl;
   friend class UsbDeviceHandleUsbfs;
   friend class UsbServiceAndroid;
   friend class UsbServiceImpl;
   friend class UsbServiceLinux;
+  friend class UsbServiceWin;
 
   void OnDisconnect();
   void HandleClosed(UsbDeviceHandle* handle);
 
   const std::string guid_;
 
   // The current device configuration descriptor. May be null if the device is
   // in an unconfigured state; if not null, it is a pointer to one of the
   // items in |descriptor_.configurations|.
   const UsbConfigDescriptor* active_configuration_ = nullptr;
 
   // Weak pointers to open handles. HandleClosed() will be called before each
   // is freed.
   std::list<UsbDeviceHandle*> handles_;
 
   base::ObserverList<Observer, true> observer_list_;
 
   DISALLOW_COPY_AND_ASSIGN(UsbDevice);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_USB_USB_DEVICE_H_