Print a warning on unexpected internal errors. 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/1378689 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Geoff Lang <geofflang@chromium.org>