Allow transitions on background-size with positionally matched keywords
This change allows CSS transitions to interpolate between lists with
matching keywords.
This affects interpolation for the following properties:
- border-image-width
This property is not animatable according to spec:
https://drafts.csswg.org/css-backgrounds-3/#the-border-image-width
- background-size
Values are now interpolable if their keywords are positionally matched:
https://github.com/w3c/csswg-drafts/commit/a5f9de921fa7834c79ee15660d9d86528bce1607
- -webkit-background-size
- -webkit-mask-size
These mirror the animation behaviour of background-size.
This change only affects CSS Transitions for the sake of a small mergable patch.
CSS Animations behaviour will be brought in line in a separate patch.
This change ensures we have compatible behaviour with other browsers for
transitioning between single length background-size values e.g.
"background-size: 50%" to "background-size: 100%"
BUG=616072
Review-Url: https://codereview.chromium.org/2027933002
Cr-Commit-Position: refs/heads/master@{#397661}
9 files changed
