`analyzer_cli` move to SDK.

pkg/analyzer_cli/test/data/strong_example.dart

+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/// This produces an error with --strong enabled, but not otherwise.
+class MyIterable extends Iterable<String> {
+  // Error: invalid override
+  Iterator<Object> get iterator => [1, 2, 3].iterator;
+}
+
+main() {
+  var i = new MyIterable().iterator..moveNext();
+  print(i.current);
+
+  // Error: type check failed
+  List<String> list = <dynamic>[1, 2, 3];
+  print(list);
+}