Add CSSSupportsRule to the base externs.
@@ -316,6 +316,23 @@ CSSStyleRule.prototype.selectorText;
*/
CSSStyleRule.prototype.style;
+/**
+ * @constructor
+ * @extends {CSSRule}
+ * @see https://www.w3.org/TR/css-conditional-3/#the-csssupportsrule-interface
+ */
+function CSSSupportsRule() {}
+
+/**
+ * @type {string}
+ */
+CSSSupportsRule.prototype.conditionText;
+
+/**
+ * @type {!CSSRuleList}
+ */
+CSSSupportsRule.prototype.cssRules;
+
/**
* @constructor
* @extends {CSSRule}
