Remove ViEImageProcess usage in VideoSendStream.

Replaces interface usage with direct calls on ViEEncoder removing a
layer of indirection. Also removing some methods from ViEImageProcess
that were only added for Video{Send,Receive}Stream usage.

BUG=1695
R=stefan@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/45319004

Cr-Commit-Position: refs/heads/master@{#9111}
8 files changed