Add device path enumeration to the new Windows USB backend.

device/usb/usb_device.cc

Index: device/usb/usb_device.cc
diff --git a/device/usb/usb_device.cc b/device/usb/usb_device.cc
index 5e25dcdea0450a5f12e542a5f082c1e52abdc0e1..70555787ca61ba491b8cae64551f50fa194f44a7 100644
--- a/device/usb/usb_device.cc
+++ b/device/usb/usb_device.cc
@@ -14,6 +14,16 @@ UsbDevice::Observer::~Observer() {}
 
 void UsbDevice::Observer::OnDeviceRemoved(scoped_refptr<UsbDevice> device) {}
 
+UsbDevice::UsbDevice()
+    : usb_version_(0),

[scheib, 2017/02/14 19:40:05]

It's fine, but did you consider using default member initializers in the
declaration? Seems more robust to future edits (hard to forget to add in member
list and constructors)

[Reilly Grant (use Gerrit), 2017/02/15 22:03:13]

Fixed. I was just waiting for another patch to land that removed all but the
guid_ field from this list.

+      device_version_(0),
+      guid_(base::GenerateGUID()),
+      device_class_(0),
+      device_subclass_(0),
+      device_protocol_(0),
+      vendor_id_(0),
+      product_id_(0) {}
+
 UsbDevice::UsbDevice(uint16_t usb_version,
                      uint8_t device_class,
                      uint8_t device_subclass,
@@ -36,8 +46,7 @@ UsbDevice::UsbDevice(uint16_t usb_version,
       vendor_id_(vendor_id),
       product_id_(product_id) {}
 
-UsbDevice::~UsbDevice() {
-}
+UsbDevice::~UsbDevice() {}
 
 void UsbDevice::CheckUsbAccess(const ResultCallback& callback) {
   // By default assume that access to the device is allowed. This is implemented