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

pkg/compiler/lib/src/js_backend/namer.dart

 // Copyright (c) 2011, 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 js_backend.namer;
 
 import 'dart:collection' show HashMap;
 
 import 'package:js_runtime/shared/embedded_names.dart' show JsGetName;
 
@@ skipping 457 matching lines @@
   jsAst.Name _literalAsyncPrefix;
   jsAst.Name _literalGetterPrefix;
   jsAst.Name _literalSetterPrefix;
   jsAst.Name _literalLazyGetterPrefix;
 
   jsAst.Name _staticsPropertyName;
 
   jsAst.Name get staticsPropertyName =>
       _staticsPropertyName ??= new StringBackedName('static');
 
-  jsAst.Name _rtiFieldName;
-  jsAst.Name get rtiFieldName => _rtiFieldName ??= new StringBackedName(r'$ti');
+  final String rtiName = r'$ti';
+
+  jsAst.Name _rtiFieldJsName;
+  jsAst.Name get rtiFieldJsName =>
+      _rtiFieldJsName ??= new StringBackedName(rtiName);
 
   // Name of property in a class description for the native dispatch metadata.
   final String nativeSpecProperty = '%';
 
   static final RegExp IDENTIFIER = new RegExp(r'^[A-Za-z_$][A-Za-z0-9_$]*$');
   static final RegExp NON_IDENTIFIER_CHAR = new RegExp(r'[^A-Za-z_0-9$]');
 
   final JavaScriptBackend backend;
   final ClosedWorld closedWorld;
   final CodegenWorldBuilder codegenWorldBuilder;
@@ skipping 123 matching lines @@
       case JsGetName.DEFAULT_VALUES_PROPERTY:
         return asName(defaultValuesField);
       case JsGetName.CALL_NAME_PROPERTY:
         return asName(callNameField);
       case JsGetName.DEFERRED_ACTION_PROPERTY:
         return asName(deferredAction);
       case JsGetName.OPERATOR_AS_PREFIX:
         return asName(operatorAsPrefix);
       case JsGetName.SIGNATURE_NAME:
         return asName(operatorSignature);
+      case JsGetName.RTI_NAME:
+        return asName(rtiName);
       case JsGetName.TYPEDEF_TAG:
         return asName(typedefTag);
+      case JsGetName.FUNCTION_TYPE_TAG:
+        return asName(functionTypeTag);
       case JsGetName.FUNCTION_TYPE_VOID_RETURN_TAG:
         return asName(functionTypeVoidReturnTag);
       case JsGetName.FUNCTION_TYPE_RETURN_TYPE_TAG:
         return asName(functionTypeReturnTypeTag);
       case JsGetName.FUNCTION_TYPE_REQUIRED_PARAMETERS_TAG:
         return asName(functionTypeRequiredParametersTag);
       case JsGetName.FUNCTION_TYPE_OPTIONAL_PARAMETERS_TAG:
         return asName(functionTypeOptionalParametersTag);
       case JsGetName.FUNCTION_TYPE_NAMED_PARAMETERS_TAG:
         return asName(functionTypeNamedParametersTag);
@@ skipping 1556 matching lines @@
   void addSuggestion(String original, String suggestion) {
     assert(!_suggestedNames.containsKey(original));
     _suggestedNames[original] = suggestion;
   }
 
   bool hasSuggestion(String original) => _suggestedNames.containsKey(original);
   bool isSuggestion(String candidate) {
     return _suggestedNames.containsValue(candidate);
   }
 }