Implement fromEnvironment on bool, int and String

tests/corelib/string_from_environment_test.dart

Index: tests/corelib/string_from_environment_test.dart
diff --git a/tests/corelib/main_test.dart b/tests/corelib/string_from_environment_test.dart
similarity index 51%
copy from tests/corelib/main_test.dart
copy to tests/corelib/string_from_environment_test.dart
index 141281196fae792229f0fe203315105f3d164794..0fa4756190231c1d90d3bd4911b72a1ab0cf047f 100644
--- a/tests/corelib/main_test.dart
+++ b/tests/corelib/string_from_environment_test.dart
@@ -1,10 +1,13 @@
 // 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.
+// VMOptions=-Da=a -Db=bb -Dc=ccc -Dd=
 
-library main_test;
 import "package:expect/expect.dart";
 
 main(List<String> args) {
-  Expect.equals(0, args.length);
+  Expect.equals('a', const String.fromEnvironment('a'));
+  Expect.equals('bb', const String.fromEnvironment('b'));
+  Expect.equals('ccc', const String.fromEnvironment('c'));
+  Expect.equals('', const String.fromEnvironment('d'));
 }