refactor(dart): Format Dart code

Use the dart formatter to clean up all pure Dart code.

Closes #4832

modules/angular2/src/router/route_config_nomalizer.dart

@@ -9,6 +9,7 @@ RouteDefinition normalizeRouteConfig(RouteDefinition config) {
 
 void assertComponentExists(Type component, String path) {
   if (component == null) {
-    throw new BaseException('Component for route "${path}" is not defined, or is not a class.');
+    throw new BaseException(
+        'Component for route "${path}" is not defined, or is not a class.');
   }
 }