Compute inverse gamma table at compile time.

This introduces skstd::index_sequence and skstd::make_index_sequence so
that these can be used in C++11. These are mostly equivalent to their
std:: counterparts. This also introduces SkMakeArray<N, C>
which is constexpr and creates a std::array with N elements with each
element being initialized with the value of C(i) where i is the index of
the element.

These are then used to create inverse gamma table at compile time. This
avoids threading issues.

BUG=skia:7187

Change-Id: I61fb10a778898652e546d54c104a08d6e6bf88d3
Reviewed-on: https://skia-review.googlesource.com/61380
Commit-Queue: Ben Wagner <bungeman@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>
3 files changed