Adds @HtmlImport with both dynamic and transformer based implementations. Still need an HtmlInliner…

test/html_import_annotation_test.dart

+// Copyright (c) 2015, 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.
+@HtmlImport(importPath)

[Siggi Cherem (dart-lang), 2015/02/12 16:49:44]

I'm surprised this works in the transformer without using the constant evaluator
(as in https://github.com/dart-lang/initialize/issues/22), am I missing
something? 

[jakemac, 2015/02/12 17:04:09]

This works but will be injected at runtime since the transformer doesn't know
how to deal with it. Again though in the next version its not an issue at all
:).

+// This one will throw a build time warning, but should still work dynamically.
+@HtmlImport('bad_import.html')
+library web_components.test.html_import_annotation;
+
+import 'dart:html';
+import 'package:initialize/initialize.dart' as init;
+import 'package:unittest/html_config.dart';
+import 'package:unittest/unittest.dart';
+import 'package:web_components/html_import_annotation.dart';
+
+const String importPath = 'my_import.html';
+
+main() {
+  useHtmlConfiguration();
+
+  test('adds import to head', () {
+    return init.run().then((_) {
+      var good = document.head.querySelector('link[href="$importPath"]');
+      expect(good.import.body.text, 'Hello world!\n');
+      var bad = document.head.querySelector('link[href="bad_import.html"]');
+      expect(bad.import, isNull);
+    });
+  });
+}