Implement fromEnvironment on bool, int and String

tests/corelib/string_from_environment_default_value.dart

Index: tests/corelib/string_from_environment_default_value.dart
diff --git a/tests/compiler/dart2js_native/is_check_test.dart b/tests/corelib/string_from_environment_default_value.dart
similarity index 62%
copy from tests/compiler/dart2js_native/is_check_test.dart
copy to tests/corelib/string_from_environment_default_value.dart
index db045025b43c3a74fcc4bfe3f987650a3a66db7e..3d236e7ea4e94b984008d72f2d254fadfb05659d 100644
--- a/tests/compiler/dart2js_native/is_check_test.dart
+++ b/tests/corelib/string_from_environment_default_value.dart
@@ -4,9 +4,8 @@
 
 import "package:expect/expect.dart";
 
-class A native "A" {}
-
 main() {
-  var a = [new Object()];
-  Expect.isFalse(a[0] is A);
+  Expect.isNull(const String.fromEnvironment('NOT_FOUND'));
+  Expect.equals('x',
+                const String.fromEnvironment('NOT_FOUND', defaultValue: 'x'));
 }