Enable constexpr for VC++ 2017

VC++ 2017 fixes the internal compiler error which prevented using
constexpr for some BlendFormula arrays, so tweak the #ifdefs to
enable constexpr for 2017.

This gets rid of two constructors and slightly shrinks chrome_child.dll


Change-Id: Ic4079b2da393ee89dd38da5bbb2d7c8ede8020e8
Reviewed-on: https://skia-review.googlesource.com/20160
Commit-Queue: Mike Klein <mtklein@chromium.org>
Reviewed-by: Mike Klein <mtklein@chromium.org>
1 file changed