Enable WebMIDI for Windows behind the flag

media/media.gyp

 # Copyright (c) 2012 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,
     # Override to dynamically link the cras (ChromeOS audio) library.
     'use_cras%': 0,
     # Option e.g. for Linux distributions to link pulseaudio directly
@@ skipping 391 matching lines @@
         'filters/wsola_internals.cc',
         'filters/wsola_internals.h',
         'midi/midi_manager.cc',
         'midi/midi_manager.h',
         'midi/midi_manager_mac.cc',
         'midi/midi_manager_mac.h',
         'midi/midi_message_queue.cc',
         'midi/midi_message_queue.h',
         'midi/midi_message_util.cc',
         'midi/midi_message_util.h',
+        'midi/midi_manager_win.cc',
+        'midi/midi_manager_win.h',
         'midi/midi_port_info.cc',
         'midi/midi_port_info.h',
         'video/capture/android/video_capture_device_android.cc',
         'video/capture/android/video_capture_device_android.h',
         'video/capture/fake_video_capture_device.cc',
         'video/capture/fake_video_capture_device.h',
         'video/capture/linux/video_capture_device_linux.cc',
         'video/capture/linux/video_capture_device_linux.h',
         'video/capture/mac/avfoundation_glue.h',
         'video/capture/mac/avfoundation_glue.mm',
@@ skipping 1205 matching lines @@
                   ],
                 }],
               ],
             }],
           ],
         },
       ],
     }],
   ],
 }