Adding Angular and dependent packages for testing

third_party/pkg/angular/lib/directive/ng_form.dart

+part of angular.directive;
+
+/**
+ * The form directive listens on submission requests and, depending,
+ * on if an action is set, the form will automatically either allow
+ * or prevent the default browser submission from occurring.
+ */
+@NgDirective(
+    selector: 'form',
+    visibility: NgDirective.CHILDREN_VISIBILITY)
+class NgForm {
+  dom.Element _element;
+  Scope _scope;
+
+  NgForm(this._scope, this._element) {
+    if(!this._element.attributes.containsKey('action')) {
+      this._element.onSubmit.listen((event) {
+        event.preventDefault();
+      });
+    }
+  }
+}