Move getDisplayMedia to MediaDevices

Following https://github.com/w3c/mediacapture-screen-share/pull/86

Bug: 326740
Change-Id: Ifb65a33a7f998563640d9f508d26d91ecb16c32f
Reviewed-on: https://chromium-review.googlesource.com/c/1313188
Reviewed-by: Henrik Boström <hbos@chromium.org>
Reviewed-by: Philip Jägenstedt <foolip@chromium.org>
Reviewed-by: Harald Alvestrand <hta@chromium.org>
Commit-Queue: Emircan Uysaler <emircan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605436}
14 files changed