Chameleon: Retry the flaky method get_display_modes()

It is about the issue crbug.com/547801. Some experiment got the result that
the first call of get_available_resolutions() or get_display_modes() always
failed. Add a retry logic to work around it. Should investigate the root
cause later.

BUG=chromium:547801
TEST=Ran the test display_ResolutionList.extended passed.

Change-Id: Ie6739f1c1b422152c4f467553b780ed676fecbc1
Reviewed-on: https://chromium-review.googlesource.com/313651
Commit-Ready: Wai-Hong Tam <[email protected]>
Tested-by: Wai-Hong Tam <[email protected]>
Reviewed-by: Kalin Stoyanov <[email protected]>
2 files changed