First shot at implementing drag&drop for Aura

ui/aura/aura.gyp

 # Copyright (c) 2011 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': {
     'chromium_code': 1,
   },
   'targets': [
     {
@@ skipping 17 matching lines @@
         'aura_switches.cc',
         'aura_switches.h',
         'cursor.h',
         'desktop_host.h',
         'desktop_host_linux.cc',
         'desktop_host_win.cc',
         'desktop_host_win.h',
         'desktop.cc',
         'desktop.h',
         'desktop_delegate.h',
+        'drag_drop_controller.h',
         'event.cc',
         'event.h',
         'event_filter.cc',
         'event_filter.h',
         'focus_manager.h',
         'hit_test.h',
         'layout_manager.cc',
         'layout_manager.h',
         'screen_aura.cc',
         'screen_aura.h',
@@ skipping 97 matching lines @@
         }],
         ['OS!="mac"', {
           'dependencies': [
             '../../chrome/chrome.gyp:packed_resources',
            ],
         }],
       ],
     },
   ],
 }