Revert of Convert device::UsbConfigDescriptor and friends to structs.

device/usb/usb_device.h

Index: device/usb/usb_device.h
diff --git a/device/usb/usb_device.h b/device/usb/usb_device.h
index a012025b35784be2a1e1f90f467e80c9d1938973..586fd19cdce706c59b50c48b3ed621b95e22ea3f 100644
--- a/device/usb/usb_device.h
+++ b/device/usb/usb_device.h
@@ -12,7 +12,7 @@
 namespace device {
 
 class UsbDeviceHandle;
-struct UsbConfigDescriptor;
+class UsbConfigDescriptor;
 
 // A UsbDevice object represents a detected USB device, providing basic
 // information about it. For further manipulation of the device, a
@@ -44,9 +44,10 @@
   // Blocking method. Must be called on FILE thread.
   virtual bool Close(scoped_refptr<UsbDeviceHandle> handle) = 0;
 
-  // Gets the UsbConfigDescriptor for the active device configuration.
+  // Lists the interfaces provided by the device and fills the given
+  // UsbConfigDescriptor.
   // Blocking method. Must be called on FILE thread.
-  virtual const UsbConfigDescriptor& GetConfiguration() = 0;
+  virtual scoped_refptr<UsbConfigDescriptor> ListInterfaces() = 0;
 
  protected:
   UsbDevice(uint16 vendor_id, uint16 product_id, uint32 unique_id)