Support "--checked" in pub run and global run.

test/global/run/runs_script_in_unchecked_mode_test.dart

 // Copyright (c) 2014, 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.
 
+import 'package:scheduled_test/scheduled_test.dart';
+
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
 
+const SCRIPT = """
 main() {
-  integration('runs a script in an activated package', () {
+  int a = true;
+  print("no checks");
+}
+""";
+
+main() {
+  integration('runs a script in unchecked mode by default', () {
     servePackages((builder) {
       builder.serve("foo", "1.0.0", contents: [
         d.dir("bin", [
-          d.file("script.dart", "main(args) => print('ok');")
+          d.file("script.dart", SCRIPT)
         ])
       ]);
     });
 
     schedulePub(args: ["global", "activate", "foo"]);
 
     var pub = pubRun(global: true, args: ["foo:script"]);
-    pub.stdout.expect("ok");
+    pub.stdout.expect("no checks");
     pub.shouldExit();
   });
 }