Adding Angular and dependent packages for testing

third_party/pkg/angular/lib/core/exception_handler.dart

+part of angular.core;
+
+/**
+ * Any uncaught exception in angular expressions is delegated to this service.
+ * The default implementation logs exceptions into console.
+ *
+ * In your application it is expected that this service is overridden with
+ * your implementation which can store the exception for later processing.
+ */
+@NgInjectableService()
+class ExceptionHandler {
+
+ /**
+  * Delegate uncaught exception for central error handling.
+  *
+  * - [error] The error which was caught.
+  * - [stack] The stacktrace.
+  * - [reason] Optional contextual information for the error.
+  */
+  call(dynamic error, dynamic stack, [String reason = '']){
+    print("$error\n$reason\nSTACKTRACE:\n$stack");
+  }
+}