update memset16/32 inlining heuristics

I spent some time looking at perf.skia.org and it looks like we can do better.

It is weird, weird, weird that on x86, we see three completely different behaviors:
  - x86 Android: inlining better for small N, custom better for large N;
  - Windows:     inlining better for large N, custom better for small N;
  - other x86:   inlining generally better

BUG=skia:4316,chromium:516426

Committed: https://skia.googlesource.com/skia/+/b68fa409fc00ce2f38e2a0fd6f9dc2379b372481

Summaries: https://perf.skia.org/#4179
All traces, log scale: https://perf.skia.org/#4180

TBR=reed@google.com
No public API changes.

Review URL: https://codereview.chromium.org/1357193002

0 files changed, 0 insertions, 0 deletions