Big merge from experimental to bleeding edge.

tests/corelib/map_keys2_test.dart

+// Copyright (c) 2011, 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.
+
+main() {
+  var map1 = { "foo": 42, "bar": 499 };
+  var map2 = {};
+  var map3 = const { "foo": 42, "bar": 499 };
+  var map4 = const {};
+  var map5 = new Map<String, int>();
+  map5["foo"] = 43;
+  map5["bar"] = 500;
+  var map6 = new Map<String, bool>();
+
+  Expect.isTrue(map1.keys is Iterable<String>);
+  Expect.isFalse(map1.keys is Iterable<bool>);
+
+  Expect.isTrue(map2.keys is Iterable<String>);
+  Expect.isFalse(map2.keys is Iterable<bool>);
+
+  Expect.isTrue(map3.keys is Iterable<String>);
+  Expect.isFalse(map3.keys is Iterable<bool>);
+
+  Expect.isTrue(map4.keys is Iterable<String>);
+  Expect.isFalse(map4.keys is Iterable<bool>);
+
+  Expect.isTrue(map5.keys is Iterable<String>);
+  Expect.isFalse(map5.keys is Iterable<bool>);
+
+  Expect.isTrue(map6.keys is Iterable<String>);
+  Expect.isFalse(map6.keys is Iterable<bool>);
+}