Adding Angular and dependent packages for testing

third_party/pkg/angular/test/io/test_files/main.dart

+library test_files.main;
+
+import 'package:angular/core/module.dart';
+
+@NgDirective(
+    children: NgAnnotation.TRANSCLUDE_CHILDREN,
+    selector:'[ng-if]',
+    map: const {'.': '=>ngIfCondition'})
+class NgIfDirective {
+  bool ngIfCondition;
+}
+
+@NgComponent(
+    selector: 'my-component',
+    map: const {
+      'attr': '@attr',
+      'expr': '=>expr'
+    },
+    template: '<div>{{ctrl.inline.template.expression}}</div>',
+    exportExpressionAttrs: const ['exported-attr'],
+    exportExpressions: const ['exported + expression']
+)
+class MyComponent {
+  @NgOneWay('another-expression')
+  String anotherExpression;
+
+  @NgCallback('callback')
+  set callback(Function) {}
+
+  set twoWayStuff(String abc) {}
+  @NgTwoWay('two-way-stuff')
+  String get twoWayStuff => null;
+}