will-change: update browser support

[paulirish]

webkit started implementing, so time for a refresher. (i'll go update MDN too)

---

Also, unrelated… but I wanted to tell someone.. here's Chrome's behavior for custom-ident's…

will-change values that trigger a compositing layer in Chrome:

• opacity
• transform, -webkit-transform
• top, left, bottom, right

source: ComputedStyle::hasWillChangeCompositingHint()

will-change values that trigger a stacking context in chrome

• opacity
• transform, -webkit-transform
• transform-style, -webkit-transform-style
• perspective, -webkit-perspective
• -webkit-mask, -webkit-mask-box-image, -webkit-clip-path, -webkit-box-reflect, -webkit-filter
• z-index
• position

source: hasWillChangeThatCreatesStackingContext

also

• AFAICT, scroll-position does nothing in Chrome currently.
• contents appears to be a compositing layer hint for whatever children are being changed.

[paulirish]

cc @aerotwist for the FYI

[paullewis]

Handy. Thanks!

[pepelsbey]

@paulirish, thank you! Merging and deploying now.

[danieltroger]

Also, unrelated… but I wanted to tell someone.. here's Chrome's behavior for custom-ident's…

For anyone else who gets linked here from MDN, here seems to be the 2022 status of this:

1. https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/core/style/computed_style.cc;drc=26f382174adc04c0d92e7dff24c6aed5d5e0246b;bpv=0;bpt=1;l=1196
2. https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/core/style/computed_style.cc;l=1133?q=CreatesStackingContext&sq=