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

device/usb/usb_service_win.cc

Index: device/usb/usb_service_win.cc
diff --git a/device/usb/usb_service_win.cc b/device/usb/usb_service_win.cc
index 131fdb3317c854a41f2b10d3020992611c8a2e25..9ee40468c8e7b1f81c03ffd53a336b84f6dc11d0 100644
--- a/device/usb/usb_service_win.cc
+++ b/device/usb/usb_service_win.cc
@@ -334,12 +334,16 @@ void UsbServiceWin::CreateDeviceObject(const std::string& device_path,
   if (!enumeration_ready())
     ++first_enumeration_countdown_;
 
-  scoped_refptr<UsbDeviceWin> device(new UsbDeviceWin(
-      device_path, hub_path, port_number, blocking_task_runner()));
+  scoped_refptr<UsbDeviceWin> device(
+      new UsbDeviceWin(device_path, hub_path, port_number, task_runner()));
   devices_by_path_[device->device_path()] = device;
+  device->ReadDescriptors(base::Bind(&UsbServiceWin::OnReadDescriptors,
+                                     weak_factory_.GetWeakPtr(), device));
+}
 
-  // TODO(reillyg): Read device descriptors.
-  DeviceReady(device, true);
+void UsbServiceWin::OnReadDescriptors(scoped_refptr<UsbDeviceWin> device,
+                                      bool success) {
+  DeviceReady(device, success);
 }
 
 void UsbServiceWin::DeviceReady(scoped_refptr<UsbDeviceWin> device,