Googletest is (at last) converging with industry-standard terminology
[1]. We previously called test suites "test cases", which was rather
confusing for folks coming from any other testing framework.

Chrome now has a googletest version that supports _TEST_SUITE_ macros
instead of _TEST_CASE_, so this CL cleans up some of the outdated usage.

[1] https://github.com/google/googletest/blob/master/googletest/docs/primer.md#beware-of-the-nomenclature

Bug: chromium:925652
Change-Id: Ia0deec0bc4216ef1adabc33985a7cbda89682608
Reviewed-on: https://chromium-review.googlesource.com/c/1477418Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Victor Costan <pwnall@chromium.org>