CSSOM bits for @supports: CSSConditionRule and CSSSupportsRule, with conditionText attribute

components/script/dom/webidls/CSSConditionRule.webidl

@@ -0,0 +1,9 @@
+/* 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-conditional/#cssconditionrule
+[Abstract, Exposed=Window]
+interface CSSConditionRule : CSSGroupingRule {
+    attribute DOMString conditionText;
+};

components/script/dom/webidls/CSSMediaRule.webidl

@@ -3,7 +3,8 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://drafts.csswg.org/cssom/#the-cssmediarule-interface
+// https://drafts.csswg.org/css-conditional/#cssmediarule
 [Exposed=Window]
-interface CSSMediaRule : CSSGroupingRule {
+interface CSSMediaRule : CSSConditionRule {
   [SameObject, PutForwards=mediaText] readonly attribute MediaList media;
 };

components/script/dom/webidls/CSSRule.webidl

@@ -31,3 +31,7 @@ partial interface CSSRule {
     const unsigned short VIEWPORT_RULE = 15;
 };
 
+// https://drafts.csswg.org/css-conditional-3/#extentions-to-cssrule-interface
+partial interface CSSRule {
+    const unsigned short SUPPORTS_RULE = 12;
+};

components/script/dom/webidls/CSSSupportsRule.webidl

@@ -0,0 +1,8 @@
+/* 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-conditional/#csssupportsrule
+[Exposed=Window]
+interface CSSSupportsRule : CSSConditionRule {
+};