Reapply 'Add runtimeType() to Object which returns canonicalized instances of Type'.

lib/compiler/implementation/world.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.
 
 class World {
   final Compiler compiler;
   final Map<ClassElement, Set<ClassElement>> subtypes;
   final Set<ClassElement> classesNeedingRti;
   final Map<ClassElement, Set<ClassElement>> rtiDependencies;
   final FunctionSet userDefinedGetters;
@@ skipping 54 matching lines @@
     while (!worklist.isEmpty()) {
       Element e = worklist.removeLast();
       Set<Element> dependencies = rtiDependencies[e];
       if (dependencies == null) continue;
       dependencies.forEach((Element other) {
         potentiallyAddForRti(other, () => worklist.add(other));
       });
     }
   }
 
-  bool needsRti(ClassElement cls) => classesNeedingRti.contains(cls);
+  bool needsRti(ClassElement cls) {
+    return classesNeedingRti.contains(cls) || compiler.enabledRuntimeType;
+  }
 
   void registerRtiDependency(Element element, Element dependency) {
     // We're not dealing with typedef for now.
     if (!element.isClass() || !dependency.isClass()) return;
     Set<ClassElement> classes =
         rtiDependencies.putIfAbsent(element, () => new Set<ClassElement>());
     classes.add(dependency);
   }
 
   void recordUserDefinedGetter(Element element) {
@@ skipping 81 matching lines @@
   final SourceString name;
 
   MemberSet(SourceString this.name) : elements = new Set<Element>();
 
   void add(Element element) {
     elements.add(element);
   }
 
   bool isEmpty() => elements.isEmpty();
 }