Add "point of interest" app for command-line testing of dart2js type information.

dart/tests/try/source_update_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 'test_try.dart';
-
-InteractionContext interaction;
-
-void main() {
-  interaction = mockTryDartInteraction();
-
-  runTests(<TestCase>[
-
-    new TestCase('Test setting full source', () {
-      clearEditorPaneWithoutNotifications();
-      mainEditorPane.appendText('Foo\nBar');
-    }, () {
-      expectSource('Foo\nBar');
-    }),
-
-    new TestCase('Test modifying a single line', () {
-      Element lastLine = mainEditorPane.lastChild;
-      lastLine.appendText('Baz');
-    }, () {
-      expectSource('Foo\nBarBaz');
-    }),
-
-  ]);
-}
-
-void expectSource(String expected) {
-  String actualSource = interaction.currentCompilationUnit.content;
-  Expect.stringEquals(expected, actualSource);
-}