Test List

https://wpt.fyi/results/css/css-transitions/transition-behavior.html?label=experimental&label=master&aligned
https://wpt.fyi/results/css/css-masking/clip-path/animations/clip-path-interpolation-discrete.html?label=experimental&label=master&aligned
https://wpt.fyi/results/css/motion/animation/offset-path-interpolation-007.html?label=experimental&label=master&aligned

Rationale

I renamed css-transitions/all-with-discrete.tentative.html as css-transitions/transition-behaivor.html because transtion-property: all is not a special case now and the spec uses transition-behavior to handle discrete transition cases, in this PR. I added some more sub-tests in transition-behaivor.html as well. For now, Gecko and WebKit passed all sub-tests.

I also added clip-path-interpolation-discrete.html and offset-path-interpolation-007.html (in this PR) to make sure we create the discrete transitions if the animation values fall back to discrete. For now, Gecko and WebKit passed all sub-tests.

Therefore, perhaps it's worth to add these three tests into @starting-style & transition-behavior focus area because the current test meta only check the parsing and serialization of transition-behavior. It's not enough obviously.