Create base::Feature for using video capture API in DevTools

Create a base::Feature for using video capture API in DevTools so we
can do finch trial independent of Viz.

Bug: 813929
Change-Id: I44da043f473d8be663931306e7e9dd296143b1c4
Reviewed-on: https://chromium-review.googlesource.com/963183
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Commit-Queue: Saman Sami <samans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543972}
6 files changed