Add GetUsbKeyCode dev interface for Pepper key events

ppapi/native_client/src/shared/ppapi_proxy/ppb_input_event.srpc

 # Copyright (c) 2011 The Native Client Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # RPC methods used to implement the PPB_InputEvent interface.
 # See ppapi/c/ppb_input_event.h for interface details.
 {
  'name': 'PpbInputEventRpc',
  'rpcs': [
           {'name': 'PPB_InputEvent_RequestInputEvents',
@@ skipping 35 matching lines @@
                       ['scroll_by_page', 'int32_t']  # PP_Bool
                      ],
            'outputs': [['resource_id', 'PP_Resource']]
           },
           {'name': 'PPB_InputEvent_CreateKeyboardInputEvent',
            'inputs': [['instance', 'PP_Instance'],  # PP_Instance
                       ['type', 'int32_t'],  # PP_InputEvent_Type
                       ['time_stamp', 'double'],  # PP_TimeTicks
                       ['modifiers', 'int32_t'],  # uint32_t
                       ['key_code', 'int32_t'],  # uint32_t
+                      ['usb_scan_code', 'int32_t'],  # uint32_t
                       ['character_text', 'char[]']  # String PP_Var
                      ],
            'outputs': [['resource_id', 'PP_Resource']]
           }
 
          ]
 }