Simplify runtime type support.

sdk/lib/_internal/compiler/implementation/js_backend/emitter.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of js_backend;
 
 /**
  * A function element that represents a closure call. The signature is copied
  * from the given element.
  */
@@ skipping 174 matching lines @@
       var field = fields[i];
       field = generateGetterSetter(field, prototype);
       str += field;
       body += "this." + field + " = " + field + ";\\n";
     }
     str += ") {" + body + "}\\n";
     str += "return " + cls + ";";
     constructor = new Function(str)();
   }
   constructor.prototype = prototype;
+  constructor.builtin\$cls = cls;
   return constructor;
 }""";
   }
 
   /** Needs defineClass to be defined. */
   String get protoSupportCheck {
     // On Firefox and Webkit browsers we can manipulate the __proto__
     // directly. Opera claims to have __proto__ support, but it is buggy.
     // So we have to do more checks.
     // Opera bug was filed as DSK-370158, and fixed as CORE-47615
@@ skipping 1529 matching lines @@
 const String HOOKS_API_USAGE = """
 // Generated by dart2js, the Dart to JavaScript compiler.
 // The code supports the following hooks:
 // dartPrint(message)   - if this function is defined it is called
 //                        instead of the Dart [print] method.
 // dartMainRunner(main) - if this function is defined, the Dart [main]
 //                        method will not be invoked directly.
 //                        Instead, a closure that will invoke [main] is
 //                        passed to [dartMainRunner].
 """;