Fix 'collection' tests and co19 dartc/dart2js status files.

tests/html/element_classes_test.dart

Index: tests/html/element_classes_test.dart
diff --git a/tests/html/element_classes_test.dart b/tests/html/element_classes_test.dart
index f499916cc49ca60bd1c2413e351c1bd1874c9837..83bb86ce44eabbb70ec826976b3c7e92f0b4cf1c 100644
--- a/tests/html/element_classes_test.dart
+++ b/tests/html/element_classes_test.dart
@@ -150,13 +150,6 @@ main() {
     expect(classes, orderedEquals(['baz', 'qux', 'quux']));
   });
 
-  test('isSubsetOf', () {
-    final classes = makeClassSet();
-    expect(classes.isSubsetOf(['foo', 'bar', 'baz'].toSet()), isTrue);
-    expect(classes.isSubsetOf(['foo', 'bar', 'baz', 'qux'].toSet()), isTrue);
-    expect(classes.isSubsetOf(['foo', 'bar', 'qux'].toSet()), isFalse);
-  });
-
   test('containsAll', () {
     final classes = makeClassSet();
     expect(classes.containsAll(['foo', 'baz'].toSet()), isTrue);