--- a/devtools/server/tests/mochitest/test_styles-applied.html
+++ b/devtools/server/tests/mochitest/test_styles-applied.html
@@ -83,17 +83,17 @@ addTest(function inheritedSystemStyles()
     // If our system stylesheets are prone to churn, this might be a fragile
     // test.  If you're here because of that I apologize, file a bug
     // and we can find a different way to test.
 
     ok(!applied[1].inherited, "Entry 1 should not be inherited");
     ok(!applied[1].rule.parentStyleSheet.system, "Entry 1 should be a system style");
     is(applied[1].rule.type, 1, "Entry 1 should be a rule style");
 
-    is(applied.length, 12, "Should have 12 rules.");
+    is(applied.length, 13, "Should have 13 rules.");
   }).then(runNextTest));
 });
 
 addTest(function noInheritedStyles() {
   promiseDone(gWalker.querySelector(gWalker.rootNode, "#test-node").then(node => {
     return gStyles.getApplied(node, { inherited: false, filter: "user" });
   }).then(applied => {
     ok(!applied[0].inherited, "Entry 0 should be uninherited");

--- a/devtools/shared/css/generated/properties-db.js
+++ b/devtools/shared/css/generated/properties-db.js
@@ -3266,17 +3266,16 @@ exports.CSS_PROPERTIES = {
       "flat",
       "flex",
       "flex-end",
       "flex-start",
       "flow-root",
       "forwards",
       "full-width",
       "geometricprecision",
-      "grayscale",
       "grid",
       "groove",
       "groupbox",
       "hanging",
       "hard-light",
       "hidden",
       "hide",
       "horizontal",
@@ -9332,16 +9331,17 @@ exports.CSS_PROPERTIES = {
 
 /**
  * A list of the pseudo elements.
  */
 exports.PSEUDO_ELEMENTS = [
   ":after",
   ":before",
   ":backdrop",
+  ":cue",
   ":first-letter",
   ":first-line",
   ":-moz-selection",
   ":-moz-focus-inner",
   ":-moz-focus-outer",
   ":-moz-list-bullet",
   ":-moz-list-number",
   ":-moz-math-anonymous",

--- a/layout/inspector/tests/test_getCSSPseudoElementNames.html
+++ b/layout/inspector/tests/test_getCSSPseudoElementNames.html
@@ -8,16 +8,17 @@
   <script type="application/javascript">
   let utils = SpecialPowers.Cc["@mozilla.org/inspector/dom-utils;1"]
                            .getService(SpecialPowers.Ci.inIDOMUtils);
 
   let expected = new Set([
     ":after",
     ":before",
     ":backdrop",
+    ":cue",
     ":first-letter",
     ":first-line",
     ":placeholder",
     ":-moz-color-swatch",
     ":-moz-focus-inner",
     ":-moz-focus-outer",
     ":-moz-list-bullet",
     ":-moz-list-number",