In many cases, the condition already explains the assertion and a string
message clutters the code without adding value. This wrapper macro is
actually very useful in such cases.

Change-Id: I44f27c1c9255f5fc80453c92565f07f8f3cbacae
Reviewed-on: https://chromium-review.googlesource.com/1216183Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55767}