Fix compilation if HAVE_WEBRTC_VIDEO is not defined.

talk/media/webrtc/webrtcvideocapturerfactory.cc

 /*
  * libjingle
  * Copyright 2014 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 14 matching lines @@
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "talk/media/webrtc/webrtcvideocapturer.h"
 #include "talk/media/webrtc/webrtcvideocapturerfactory.h"
 #include "webrtc/base/scoped_ptr.h"
 
 namespace cricket {
 
 VideoCapturer* WebRtcVideoDeviceCapturerFactory::Create(const Device& device) {
+#ifdef HAVE_WEBRTC_VIDEO
   rtc::scoped_ptr<WebRtcVideoCapturer> capturer(
       new WebRtcVideoCapturer());
   if (!capturer->Init(device)) {
-    return NULL;
+    return nullptr;
   }
   return capturer.release();
+#else
+  return nullptr;
+#endif
 }
 
 }  // namespace cricket