Chameleon: Save screen as a RGB filetype instad of a PNG file

Recently, we saw a random <Unhandled IOError: decoder zip not available>
error while converting a PNG file to RGB format. Not sure the root cause.
It is better to skip handling the PNG filetype and save as a raw RGB file.

BUG=chromium:402724
TEST=Ran display_Resolution.mirrored test on daisy_spring passed.

Change-Id: I42125a57c3b9a9fda67335423868274ca7b8c5d5
Reviewed-on: https://chromium-review.googlesource.com/211924
Reviewed-by: Hung-ying Tyan <tyanh@chromium.org>
Commit-Queue: Wai-Hong Tam <waihong@chromium.org>
Tested-by: Wai-Hong Tam <waihong@chromium.org>
1 file changed