Implement fromEnvironment on bool, int and String

tests/corelib/int_from_environment_test.dart

Index: tests/corelib/int_from_environment_test.dart
diff --git a/tests/corelib/int_from_environment_test.dart b/tests/corelib/int_from_environment_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..f842fddb4c328530545477984ff4f4045f9b8ec9
--- /dev/null
+++ b/tests/corelib/int_from_environment_test.dart
@@ -0,0 +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.
+// SharedOptions=-Da=1 -Db=-12 -Dc=0x123 -Dd=-0x1234
+
+import "package:expect/expect.dart";
+
+main() {
+  Expect.equals(1, const int.fromEnvironment('a'));
+  Expect.equals(-12, const int.fromEnvironment('b'));
+  Expect.equals(0x123, const int.fromEnvironment('c'));
+  Expect.equals(-0x1234, const int.fromEnvironment('d'));
+}