Remove deprecated mappedBy.

tests/html/streams_test.dart

 library streams_test;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_config.dart';
 import 'dart:async';
 import 'dart:html';
 
 class StreamHelper {
   var _a;
   StreamHelper() {
     _a = new TextInputElement();
@@ skipping 173 matching lines @@
   });
 
   test('asBroadcastStream', () {
     stream.asBroadcastStream().listen((_) {});
   });
 
   test('where', () {
     stream.where((_) => true).listen((_) {});
   });
 
-  test('mappedBy', () {
+  test('map', () {
     stream.map((_) => null).listen((_) {});
   });
 
   test('reduce', () {
     stream.reduce(null, (a, b) => null).then((_) {});
   });
 
   test('contains', () {
     stream.contains((_) => true).then((_) {});
   });
@@ skipping 71 matching lines @@
   });
 
   test('singleMatching', () {
     stream.singleMatching((_) => true).then((_) {});
   });
 
   test('elementAt', () {
     stream.elementAt(0).then((_) {});
   });
 }