Fixing "control reaches end of non-void function" compile warning.

webrtc/api/mediatypes.cc

 /*
  *  Copyright 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 10 matching lines @@
 
 std::string MediaTypeToString(MediaType type) {
   switch (type) {
     case MEDIA_TYPE_AUDIO:
       return webrtc::MediaStreamTrackInterface::kAudioKind;
     case MEDIA_TYPE_VIDEO:
       return webrtc::MediaStreamTrackInterface::kVideoKind;
     case MEDIA_TYPE_DATA:
       return kMediaTypeData;
   }
+  FATAL();
   // Not reachable; avoids compile warning.
-  FATAL();
+  return "";
 }
 
 MediaType MediaTypeFromString(const std::string& type_str) {
   if (type_str == webrtc::MediaStreamTrackInterface::kAudioKind) {
     return MEDIA_TYPE_AUDIO;
   } else if (type_str == webrtc::MediaStreamTrackInterface::kVideoKind) {
     return MEDIA_TYPE_VIDEO;
   } else if (type_str == kMediaTypeData) {
     return MEDIA_TYPE_DATA;
-  } else {
-    FATAL();
   }
+  FATAL();
+  // Not reachable; avoids compile warning.
+  return static_cast<MediaType>(-1);
 }
 
 }  // namespace cricket