The error message can be dropped when converting angle::Result to egl::Error.
This makes sure something is always printed when we get an unexpected error.

BUG=914911

Change-Id: Icc8b06b1c13e3ea83287da5a217f4c8bc218deec
Reviewed-on: https://chromium-review.googlesource.com/c/1378689Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>