Bug 1824526 - Ship color-mix. r=dholbert

We pass all the tests, except one (gamut-mapping.html) which Chromium
also fails and which is still under active discussion, but leaning
towards our current behavior: https://github.com/w3c/csswg-drafts/issues/8444

Differential Revision: https://phabricator.services.mozilla.com/D174369

modules/libpref/init/StaticPrefList.yaml

@@ -8466,14 +8466,14 @@
 # Is support for color-mix on content enabled?
 - name: layout.css.color-mix.enabled
   type: RelaxedAtomicBool
-  value: @IS_NIGHTLY_BUILD@
+  value: true
   mirror: always
   rust: true
 
 # Is support for color-mix with non-SRGB color spaces on content enabled?
 - name: layout.css.color-mix.color-spaces.enabled
   type: RelaxedAtomicBool
-  value: @IS_NIGHTLY_BUILD@
+  value: true
   mirror: always
   rust: true
 

testing/web-platform/meta/css/css-color/parsing/color-invalid-color-mix-function.html.ini

@@ -1,3 +0,0 @@
-[color-invalid-color-mix-function.html]
-  expected:
-    if (os == "android") and fission: [OK, TIMEOUT]