Reland "reenable mouse_cursor_monitor tests on linux"

This is a reland of 79098821a23f9de49f70cb3794b51e2730bffa01
with changes to disable the tests when not building with X11 support.

TBR=sergeyu@chromium.org
Original change's description:
> reenable mouse_cursor_monitor tests on linux
>
> BUG=webrtc:3245
>
> Change-Id: Ibf9cd929b22a0a519950621da46eb9f5b3febd73
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/181367
> Reviewed-by: Tommi <tommi@webrtc.org>
> Reviewed-by: Sergey Ulanov <sergeyu@google.com>
> Commit-Queue: Tommi <tommi@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#31940}

BUG=webrtc:3245

Change-Id: I882e08f6f425df357f16fa4db25dcdf79db1f367
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/181882
Commit-Queue: Philipp Hancke <philipp.hancke@googlemail.com>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32047}