Remove type of panningModelType "soundfield".

Source/platform/audio/Panner.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * 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
@@ skipping 33 matching lines @@
 
     switch (model) {
     case PanningModelEqualPower:
         panner = adoptPtr(new EqualPowerPanner(sampleRate));
         break;
 
     case PanningModelHRTF:
         panner = adoptPtr(new HRTFPanner(sampleRate, databaseLoader));
         break;
 
-    // FIXME: sound field panning is not yet implemented...
-    case PanningModelSoundField:
     default:
         ASSERT_NOT_REACHED();
         return nullptr;
     }
 
     return panner.release();
 }
 
 } // namespace WebCore
 
 #endif // ENABLE(WEB_AUDIO)