Add use-counter and WebDX feature mapping for revert.

Change-Id: I8885c31ef646470b29f9171980162f70bc4be662
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5998699
Reviewed-by: Rune Lillesveen <[email protected]>
Reviewed-by: Shunya Shishido <[email protected]>
Commit-Queue: Steinar H Gunderson <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1380258}

Author: Steinar H. Gunderson

css/css-cascade/WEB_FEATURES.yml

@@ -6,3 +6,6 @@ features:
   files:
   - at-scope-*
   - scope-*
+- name: revert
+  files:
+  - revert-val-*