Fix unsigned/signed comparison error due to r4729.

Fix it for real by switching to ints rather than casting.

TBR=xians

Review URL: https://webrtc-codereview.appspot.com/2191009

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@4730 4adac7df-926f-26a2-2b94-8c16560cd09d
2 files changed