Simplify SkCpu.cpp preprocessor guards.

We have a couple ways to detect CPU features on ARM:
  - on ARMv8, getauxval(AT_HWCAP)
  - on ARMv7, getauxval(AT_HWCAP) and cpu-features.h

This guards each of these methods with preprocessor guards to match
exactly when we can use them.  Today they're sort of a mix of that and
higher level expectations about particular build and operating systems.

I'm looking into doing this directly by reading CPU registers,
much like we do for x86 further up the file.

None of this is super important right now, so as long as we don't decide
that we have these features when we don't, things will be fine.  It's no
big deal for now if we fail to detect them.

Change-Id: I3b7768483086d0f3f4f6516b754c3ea5ec2d03e5
Reviewed-on: https://skia-review.googlesource.com/8182
Reviewed-by: Chinmay Garde <chinmaygarde@google.com>
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>
1 file changed