GitLab

Update navigator.requestMediaKeySystemAccess() to support querying for
encryption scheme support. This is based on
https://github.com/WICG/encrypted-media-encryption-scheme/blob/master/explainer.md.

BUG=657957
TEST=new layout and browser tests pass

Change-Id: I5ba39861bab673a61dd65c12fe82d6ba3bd63ddb
Reviewed-on: https://chromium-review.googlesource.com/959459Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Nate Chapin <japhet@chromium.org>
Reviewed-by: Xiaohan Wang <xhwang@chromium.org>
Commit-Queue: John Rummell <jrummell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567105}