Support basic immutable CSSOM

components/script/dom/webidls/CSSKeyframesRule.webidl

@@ -0,0 +1,14 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// https://drafts.csswg.org/css-animations/#interface-csskeyframesrule
+[Exposed=(Window,Worker)]
+interface CSSKeyframesRule : CSSRule {
+  //          attribute DOMString   name;
+  // readonly attribute CSSRuleList cssRules;
+
+  // void            appendRule(DOMString rule);
+  // void            deleteRule(DOMString select);
+  // CSSKeyframeRule? findRule(DOMString select);
+};