Don't use magic strings/properties to communicate between compiler and runtime.

pkg/compiler/lib/src/js_emitter/class_stub_generator.dart

 // Copyright (c) 2014, 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.
 
 library dart2js.js_emitter.class_stub_generator;
 
 import '../common/names.dart' show Identifiers;
 import '../compiler.dart' show Compiler;
 import '../elements/entities.dart';
 import '../js/js.dart' as jsAst;
@@ skipping 22 matching lines @@
     // TODO(sra): Implement placeholders in VariableDeclaration position:
     //
     //     String constructorName = namer.getNameOfClass(classElement);
     //     return js.statement('function #(#) { #; }',
     //        [ constructorName, fields,
     //            fields.map(
     //                (name) => js('this.# = #', [name, name]))]));
     var typeParameters = const <jsAst.Parameter>[];
     var typeInits = const <jsAst.Expression>[];
     if (hasRtiField) {
-      String parameterName = r'$ti';
+      String parameterName = namer.rtiName;
       typeParameters = parameterName;
-      typeInits = js('this.# = #', [namer.rtiFieldName, parameterName]);
+      typeInits = js('this.# = #', [namer.rtiFieldJsName, parameterName]);

[sra1, 2017/02/22 04:23:52]

This is the place I was telling you about.
See https://github.com/dart-lang/sdk/issues/28727
This code diff is from before the bug fix.

[floitsch, 2017/02/22 12:58:06]

Done.

     }
     return js('function(#, #) { #; #; this.#();}', [
       fields,
       typeParameters,
       fields.map((name) => js('this.# = #', [name, name])),
       typeInits,
       namer.deferredAction
     ]);
   }
 
@@ skipping 257 matching lines @@
               if (cache === void 0) cache = #tearOff(
                   this, funcs, reflectionInfo, true, [], name).prototype;
               return cache;
             }
           : tearOffGetter(funcs, reflectionInfo, name, isIntercepted);
     }''',
       {'tearOff': tearOffAccessExpression});
 
   return <jsAst.Statement>[tearOffGetter, tearOff];
 }