Both lazy initialization and static initialization (via static
initializer) are bad. Fortunately, the arrays we are constructing are
constant anyway, so we can just compute them at compile time. This is
enforced by making them constexpr.
This also saves all code needed for the initialization, and makes
accesses to the tables faster, as they don't need any atomic operations
(via LazyInstance).

R=ahaas@chromium.org

Change-Id: I7d3ba9b0f2602f596a6c71c8c567e0d1bc306268
Reviewed-on: https://chromium-review.googlesource.com/517083
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45589}