Part one of Converting DOMList types like FooList to List<Foo>.

tests/html/css_rule_list_test.dart

+#library('CSSRuleListTest');
+#import('../../pkg/unittest/unittest.dart');
+#import('../../pkg/unittest/html_config.dart');
+#import('dart:html');
+
+main() {
+
+  useHtmlConfiguration();
+
+  test("ClientRectList test", () {
+    var sheet = document.styleSheets[0];
+    List<CSSRule> rulesList = sheet.cssRules;
+    Expect.isTrue(rulesList is List<CSSRule>);
+  });
+}