Implement fromEnvironment on bool, int and String

tests/corelib/string_from_environment2_test.dart

Index: tests/corelib/string_from_environment2_test.dart
diff --git a/tests/corelib/list_filled_type_argument_test.dart b/tests/corelib/string_from_environment2_test.dart
similarity index 52%
copy from tests/corelib/list_filled_type_argument_test.dart
copy to tests/corelib/string_from_environment2_test.dart
index 6d361cc05601351f5f34641de2c0c962c67442a5..b6d81b816d7499b03d86c19ffb369382f3afe83f 100644
--- a/tests/corelib/list_filled_type_argument_test.dart
+++ b/tests/corelib/string_from_environment2_test.dart
@@ -1,11 +1,12 @@
 // Copyright (c) 2013, 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.
+// SharedOptions=-Da=a -Da=bb -Db=bb -Dc=ccc -Da=ccc -Db=ccc
 
 import "package:expect/expect.dart";
 
 main() {
-  var a = new List<int>.filled(42, 42);
-  Expect.isTrue(a is List<int>);
-  Expect.isFalse(a is List<String>);
+  Expect.equals('ccc', const String.fromEnvironment('a'));
+  Expect.equals('ccc', const String.fromEnvironment('b'));
+  Expect.equals('ccc', const String.fromEnvironment('c'));
 }