Start to vectorize SkTileGrid.

This adds Sk4x.h to help.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/90c7992bfc6330f070f7704d63372a0ec8410170

CQ_EXTRA_TRYBOTS=client.skia:Test-Ubuntu12-ShuttleA-GTX660-x86-Debug-Trybot

Review URL: https://codereview.chromium.org/634543004
8 files changed