CSSTransitionDiscrete: implement transition-animation-type

[chromium-wpt-export-bot]

This is being discussed here:
w3c/csswg-drafts#8857
The name and values of the property are still under discussion.

This patch does not implement the transition shorthand integration, I'm
going to do that next.

Fixed: 1450870
Bug: 1453112
Change-Id: I808cf6bc090ca0f99229eb4a9d9c3c28ccf22afc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4616155
Commit-Queue: Robert Flack <flackr@chromium.org>
Commit-Queue: Joey Arhar <jarhar@chromium.org>
Auto-Submit: Joey Arhar <jarhar@chromium.org>
Reviewed-by: Robert Flack <flackr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1168211}

[wpt-pr-bot]

The review process for this patch is being conducted in the Chromium project.

[WeizhongX]

WPT Command: python3 ./wpt run --channel=nightly --verify --verify-no-chaos-mode --verify-repeat-loop=0 --verify-repeat-restart=10 --github-checks-text-file=/home/test/artifacts/checkrun.md --affected base_head --log-mach-level=info --log-mach=- -y --no-pause --no-restart-on-unexpected --install-fonts --no-headless --verify-log-full --binary=/home/test/build/firefox/firefox firefox

Some affected tests had inconsistent (flaky) results:

Unstable results

Test	Subtest	Results	Messages
/css/css-content/content-no-interpolation.html		OK: 9/10, TIMEOUT: 1/10
/css/css-content/content-no-interpolation.html	CSS Transitions: property from [initial] to ["b"] at (-0.3) should be ["b"]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	CSS Transitions: property from [initial] to ["b"] at (0) should be ["b"]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	CSS Transitions: property from [initial] to ["b"] at (0.3) should be ["b"]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	CSS Transitions: property from [initial] to ["b"] at (0.5) should be ["b"]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	CSS Transitions: property from [initial] to ["b"] at (0.6) should be ["b"]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	CSS Transitions: property from [initial] to ["b"] at (1) should be ["b"]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	CSS Transitions: property from [initial] to ["b"] at (1.5) should be ["b"]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	CSS Transitions with transition: all: property from [initial] to ["b"] at (-0.3) should be ["b"]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	CSS Transitions with transition: all: property from [initial] to ["b"] at (0) should be ["b"]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	CSS Transitions with transition: all: property from [initial] to ["b"] at (0.3) should be ["b"]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	CSS Transitions with transition: all: property from [initial] to ["b"] at (0.5) should be ["b"]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	CSS Transitions with transition: all: property from [initial] to ["b"] at (0.6) should be ["b"]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	CSS Transitions with transition: all: property from [initial] to ["b"] at (1) should be ["b"]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	CSS Transitions with transition: all: property from [initial] to ["b"] at (1.5) should be ["b"]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	CSS Animations: property from [initial] to ["b"] at (-0.3) should be [initial]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	CSS Animations: property from [initial] to ["b"] at (0) should be [initial]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	CSS Animations: property from [initial] to ["b"] at (0.3) should be [initial]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	CSS Animations: property from [initial] to ["b"] at (0.5) should be ["b"]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	CSS Animations: property from [initial] to ["b"] at (0.6) should be ["b"]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	CSS Animations: property from [initial] to ["b"] at (1) should be ["b"]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	CSS Animations: property from [initial] to ["b"] at (1.5) should be ["b"]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	Web Animations: property from [initial] to ["b"] at (-0.3) should be [initial]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	Web Animations: property from [initial] to ["b"] at (0) should be [initial]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	Web Animations: property from [initial] to ["b"] at (0.3) should be [initial]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	Web Animations: property from [initial] to ["b"] at (0.5) should be ["b"]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	Web Animations: property from [initial] to ["b"] at (0.6) should be ["b"]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	Web Animations: property from [initial] to ["b"] at (1) should be ["b"]	PASS: 9/10, MISSING: 1/10
/css/css-content/content-no-interpolation.html	Web Animations: property from [initial] to ["b"] at (1.5) should be ["b"]	PASS: 9/10, MISSING: 1/10

These may be pre-existing or new flakes. Please try to reproduce (see the above WPT command, though some flags may not be needed when running locally) and determine if your change introduced the flake. If you are unable to reproduce the problem, please tag @web-platform-tests/wpt-core-team in a comment for help.

[WeizhongX]

submit crbug.com/1464305. @jcscottiii @KyleJu can you help admin merge this? thanks!