Fix compilation if HAVE_WEBRTC_VIDEO is not defined.

talk/libjingle.gyp

 #
 # libjingle
 # Copyright 2012 Google Inc.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are met:
 #
 #  1. Redistributions of source code must retain the above copyright notice,
 #     this list of conditions and the following disclaimer.
 #  2. Redistributions in binary form must reproduce the above copyright notice,
@@ skipping 522 matching lines @@
         'media/devices/devicemanager.cc',
         'media/devices/devicemanager.h',
         'media/devices/dummydevicemanager.h',
         'media/devices/filevideocapturer.cc',
         'media/devices/filevideocapturer.h',
         'media/devices/videorendererfactory.h',
         'media/devices/yuvframescapturer.cc',
         'media/devices/yuvframescapturer.h',
         'media/sctp/sctpdataengine.cc',
         'media/sctp/sctpdataengine.h',
+        'media/webrtc/nullwebrtcvideoengine.h',
         'media/webrtc/simulcast.cc',
         'media/webrtc/simulcast.h',
         'media/webrtc/webrtccommon.h',
         'media/webrtc/webrtcmediaengine.cc',
         'media/webrtc/webrtcmediaengine.h',
         'media/webrtc/webrtcmediaengine.cc',
         'media/webrtc/webrtcvideocapturer.cc',
         'media/webrtc/webrtcvideocapturer.h',
         'media/webrtc/webrtcvideocapturerfactory.h',
         'media/webrtc/webrtcvideocapturerfactory.cc',
@@ skipping 271 matching lines @@
         'app/webrtc/webrtcsdp.cc',
         'app/webrtc/webrtcsdp.h',
         'app/webrtc/webrtcsession.cc',
         'app/webrtc/webrtcsession.h',
         'app/webrtc/webrtcsessiondescriptionfactory.cc',
         'app/webrtc/webrtcsessiondescriptionfactory.h',
       ],
     },  # target libjingle_peerconnection
   ],
 }