Add MediaAccessHandler for getDisplayMedia()

This CL adds a new permission handler for getDisplayMedia(). It uses
DesktopMediaPickerFactoryImpl as common implementation to trigger the
same picker UI as extensions. It also adds unit test that exercises
the new code path.

Bug: 326740
Change-Id: I3007124226d2b017ba06877a1bbcc87f3bc2f9a3
Reviewed-on: https://chromium-review.googlesource.com/1163533
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Reviewed-by: Xiangjun Zhang <xjz@chromium.org>
Reviewed-by: Weiyong Yao <braveyao@chromium.org>
Commit-Queue: Emircan Uysaler <emircan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582835}
16 files changed