Recommit changing List.skip/take/revert returns Iterable and remove mappedBy.

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 89434fcbc696fe1c49ede805937536cdd6508b8c..966e5eb14170816fade0d26545dfd711d965a336 100644
--- a/tests/html/element_classes_test.dart
+++ b/tests/html/element_classes_test.dart
@@ -66,7 +66,7 @@ main() {
     expect(classes, unorderedEquals(['foo', 'bar', 'baz']));
   });
 
-  test('mappedBy', () {
+  test('map', () {
     expect(makeClassSet().map((c) => c.toUpperCase()).toList(),
         unorderedEquals(['FOO', 'BAR', 'BAZ']));
   });