We still were using the old cassert code, with a boolean return
value on our initialization code. We can make use of the gtest
macros and helpers to check for a successful init or GL errors.

BUG=476658

Change-Id: I09cbb3d40748cbeaf530ae8f23fb8a1b07e7611f
Reviewed-on: https://chromium-review.googlesource.com/265837Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Brandon Jones <bajones@chromium.org>