Style and return value changes. No impact externally, since audio_processing, audio_conference_mixer and audio_coding either already assumes 'int' as return value, assumes nothing or doesn't take care of the return value. TESTS=vad_unittests, audioproc_unittest Review URL: https://webrtc-codereview.appspot.com/374006 git-svn-id: http://webrtc.googlecode.com/svn/trunk@1581 4adac7df-926f-26a2-2b94-8c16560cd09d