Add support for reading USB descriptors to the new Windows backend.

device/usb/usb_device_win.h

 // Copyright 2017 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_WIN_H_
 #define DEVICE_USB_USB_DEVICE_WIN_H_
 
 #include <string>
 
 #include "base/macros.h"
 #include "base/threading/thread_checker.h"
 #include "device/usb/usb_device.h"
 
 namespace base {
 class SequencedTaskRunner;
 }
 
 namespace device {
 
+struct UsbDeviceDescriptor;
+
 class UsbDeviceWin : public UsbDevice {
  public:
   // UsbDevice implementation:
   void Open(const OpenCallback& callback) override;
 
  protected:
   friend class UsbServiceWin;
   friend class UsbDeviceHandleWin;
 
   // Called by UsbServiceWin only;
   UsbDeviceWin(const std::string& device_path,
                const std::string& hub_path,
                int port_number,
                scoped_refptr<base::SequencedTaskRunner> task_runner);
 
   ~UsbDeviceWin() override;
 
   const std::string& device_path() const { return device_path_; }
   int port_number() const { return port_number_; }
 
+  // Opens the device's parent hub in order to read the device, configuration
+  // and string descriptors.
+  void ReadDescriptors(const base::Callback<void(bool)>& callback);
+
+ private:
+  void OpenOnBlockingThread(const OpenCallback& callback);
+  void OnReadDescriptors(const base::Callback<void(bool)>& callback,
+                         scoped_refptr<UsbDeviceHandle> device_handle,
+                         std::unique_ptr<UsbDeviceDescriptor> descriptor);
+  void OnReadStringDescriptors(
+      const base::Callback<void(bool)>& callback,
+      scoped_refptr<UsbDeviceHandle> device_handle,
+      std::unique_ptr<std::map<uint8_t, base::string16>> string_map);
+
  private:
   base::ThreadChecker thread_checker_;
 
   const std::string device_path_;
   const std::string hub_path_;
   const int port_number_;
 
   scoped_refptr<base::SequencedTaskRunner> task_runner_;
   scoped_refptr<base::SequencedTaskRunner> blocking_task_runner_;
 
   DISALLOW_COPY_AND_ASSIGN(UsbDeviceWin);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_USB_USB_DEVICE_WIN_H_