Originally we wrote this in C++14 constexpr,
but because this is used from public headers, we can't use
C++14 yet. Now a somewhat sillier looking C++11 version.
All the old tests still pass, and one new added.
Updated the comments a bit for correctness and readability.
Change-Id: I99c01e1346c1a5a36278cc08f30538112e5259aa
Reviewed-on: https://skia-review.googlesource.com/134425
Commit-Queue: Mike Klein <mtklein@chromium.org>
Commit-Queue: Ben Wagner <bungeman@google.com>
Auto-Submit: Mike Klein <mtklein@chromium.org>
Reviewed-by: Ben Wagner <bungeman@google.com>
009f51e43f