[usb_gadget p13] Replace LUFA with UsbTestGadget in HidConnection tests.

tools/usb_gadget.gyp

 # 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.
 
 {
   'variables': {
     'usb_gadget_files': [
       'usb_gadget/__init__.py',
       'usb_gadget/__main__.py',
       'usb_gadget/default_gadget.py',
       'usb_gadget/gadget.py',
       'usb_gadget/hid_constants.py',
       'usb_gadget/hid_descriptors.py',
+      'usb_gadget/hid_echo_gadget.py',
       'usb_gadget/hid_gadget.py',
       'usb_gadget/keyboard_gadget.py',
       'usb_gadget/linux_gadgetfs.py',
       'usb_gadget/mouse_gadget.py',
       'usb_gadget/server.py',
       'usb_gadget/usb_constants.py',
       'usb_gadget/usb_descriptors.py',
     ],
     'usb_gadget_package': '<(PRODUCT_DIR)/usb_gadget.zip',
     'usb_gadget_package_hash': '<(PRODUCT_DIR)/usb_gadget.zip.md5',
@@ skipping 17 matching lines @@
             'python', 'usb_gadget/package.py',
             '--zip-file', '<(usb_gadget_package)',
             '--hash-file', '<(usb_gadget_package_hash)',
             '<@(usb_gadget_files)',
           ]
         }
       ]
     }
   ]
 }