autotest: implement get_display_resolution for freon.

BUG=chromium:413144
TEST=verify that get_display_resolution returns 2560, 1700 on link_freon

Change-Id: I34870a1504c78a97f46ab5a4d7b10f67efc85151
Reviewed-on: https://chromium-review.googlesource.com/223384
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>
Commit-Queue: Haixia Shi <hshi@chromium.org>
Tested-by: Haixia Shi <hshi@chromium.org>
Reviewed-by: Ilja Friedel <ihf@chromium.org>
1 file changed