Enable CPU adaptation by default.

WebRtcVideoEngine2 doesn't support CPU-monitor-based adaptation and as
such requires encoder-time-based CPU adaptation to perform any
adaptation at all.

BUG=4536
R=asapersson@webrtc.org, mflodman@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/49679004

Cr-Commit-Position: refs/heads/master@{#9001}
2 files changed