Roll Observatory packages and add a roll script

packages/polymer_expressions/example/example.dart

+// 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.
+
+import 'dart:html';
+
+import 'package:polymer_expressions/polymer_expressions.dart';
+import 'package:template_binding/template_binding.dart' show templateBind;
+
+// We use mirrors for illustration purposes, but ideally we would generate a
+// static configuration with smoke/static.dart.
+import 'package:smoke/mirrors.dart';
+
+// Since we use smoke/mirrors, we need to preserve symbols used in the template.
+// This includes String.startsWith, List.take, and Person.
+@MirrorsUsed(targets: const [String, List, Person])
+import 'dart:mirrors';
+
+import 'person.dart';
+
+main() {
+  useMirrors();
+  var john = new Person('John', 'Messerly', ['A', 'B', 'C']);
+  var justin = new Person('Justin', 'Fagnani', ['D', 'E', 'F']);
+  var globals = {
+    'uppercase': (String v) => v.toUpperCase(),
+    'people': [john, justin],
+  };
+
+  templateBind(querySelector('#test'))
+      ..bindingDelegate = new PolymerExpressions(globals: globals)
+      ..model = john;
+
+  templateBind(querySelector('#test2')).model = john;
+}