Adding Angular and dependent packages for testing

third_party/pkg/angular/lib/mock/probe.dart

+part of angular.mock;
+
+/*
+ * Use Probe directive to capture the Scope, Injector and Element from any DOM
+ * location into root-scope. This is useful for testing to get a hold of
+ * any directive.
+ *
+ *    <div some-directive probe="myProbe">..</div>
+ *
+ *    rootScope.myProbe.directive(SomeAttrDirective);
+ */
+@NgDirective(selector: '[probe]')
+class Probe implements NgDetachAware {
+  final Scope scope;
+  final Injector injector;
+  final Element element;
+  final NodeAttrs _attrs;
+
+  Probe(this.scope, this.injector, this.element, this._attrs) {
+    scope.$root[_attrs['probe']] = this;
+  }
+
+  detach() => scope.$root[_attrs['probe']] = null;
+
+  /**
+   * Retrieve a Directive at the current element.
+   */
+  directive(Type type) => injector.get(type);
+}
+