Dynamic resolution change for VP8 HW encode.

Off by default for now.

BUG=
R=glaznev@webrtc.org, stefan@webrtc.org
TBR=mflodman@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/45849004

Cr-Commit-Position: refs/heads/master@{#9045}
17 files changed