Adding Angular and dependent packages for testing

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

+part of angular.directive;
+
+/**
+ * The ngBind attribute tells Angular to replace the text content of the
+ * specified HTML element with the value of a given expression, and to update
+ * the text content when the value of that expression changes.
+ *
+ * Typically, you don't use ngBind directly, but instead you use the double
+ * curly markup like {{ expression }} which is similar but less verbose.
+ *
+ * It is preferrable to use ngBind instead of {{ expression }} when a template
+ * is momentarily displayed by the browser in its raw state before Angular
+ * compiles it. Since ngBind is an element attribute, it makes the bindings
+ * invisible to the user while the page is loading.
+ *
+ * An alternative solution to this problem would be using the ngCloak directive.
+ */
+@NgDirective(
+  selector: '[ng-bind]',
+  map: const {'ng-bind': '=>value'})
+class NgBindDirective {
+  dom.Element element;
+
+  NgBindDirective(this.element);
+
+  set value(value) => element.text = value == null ? '' : value.toString();
+}