Moved the filter calculation from analyze to process in ns_core

It makes sense to have it there if the analyze and process methods are called in different stages.
Tested over the entire QA set for bit exactness.

BUG=webrtc:3811
R=bjornv@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/29549004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@7287 4adac7df-926f-26a2-2b94-8c16560cd09d