feat(parser): allows users install custom AST transformers

Closes #5382

modules_dart/transform/lib/src/transform/common/ng_compiler.dart

@@ -22,8 +22,9 @@ TemplateCompiler createTemplateCompiler(AssetReader reader,
   var _htmlParser = new HtmlParser();
   var _urlResolver = const TransformerUrlResolver();
 
+  // TODO(yjbanov): add router AST transformer when ready
   var templateParser = new TemplateParser(new ng.Parser(new ng.Lexer()),
-      new DomElementSchemaRegistry(), _htmlParser);
+      new DomElementSchemaRegistry(), _htmlParser, null);
 
   var cdCompiler = changeDetectionConfig != null
       ? new ChangeDetectionCompiler(changeDetectionConfig)