Made external codec test compile and pass. BUG=961 TEST=Uncomment #define WEBRTC_VIDEO_ENGINE_EXTERNAL_CODEC_API in engine_configurations.h. Should build and extended codec test pass. Review URL: https://webrtc-codereview.appspot.com/901005 git-svn-id: http://webrtc.googlecode.com/svn/trunk/src@2937 4adac7df-926f-26a2-2b94-8c16560cd09d