Add a feature guard to implement CrOS VA-API JPEG decode acceleration.

This CL creates a base::Feature flag in content to guard the
implementation of decode acceleration of JPEG images (as opposed to
camera captures) in Chrome OS using the VA-API.

Bug: 868400
Change-Id: I103a78bc9547862620fea59fb423582226f03d59
Reviewed-on: https://chromium-review.googlesource.com/1180292
Commit-Queue: Andres Calderon Jaramillo <[email protected]>
Reviewed-by: Avi Drissman <[email protected]>
Reviewed-by: Miguel Casas <[email protected]>
Cr-Commit-Position: refs/heads/master@{#584606}
6 files changed