Delay Estimator: Minor refactoring and added a setter function.

* Replaced the lookahead input parameter at Create() with a setter. This makes it slightly more user friendly.
* Changed the buffer shifting in SoftReset... to become more readable.

TESTED=trybots, modules_unittests
R=aluebs@webrtc.org, andrew@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/11029004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@5836 4adac7df-926f-26a2-2b94-8c16560cd09d
7 files changed