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

lib/compiler/implementation/enqueue.dart

Index: lib/compiler/implementation/enqueue.dart
diff --git a/lib/compiler/implementation/enqueue.dart b/lib/compiler/implementation/enqueue.dart
index 6d6f40c6400de2472407741849db1a1d7fbd78ca..4a4b3530618480f43f0728e3cd928b74278471b5 100644
--- a/lib/compiler/implementation/enqueue.dart
+++ b/lib/compiler/implementation/enqueue.dart
@@ -107,6 +107,11 @@ class Enqueuer {
 
     queue.add(new WorkItem(element, elements, itemCompilationContextCreator()));
 
+    // Enable runtime type support if we discover a method called runtimeType.
+    if (element.isFunction() && element.name == Compiler.RUNTIME_TYPE) {
+      compiler.enabledRuntimeType = true;
+    }
+
     // Enable isolate support if we start using something from the
     // isolate library.
     LibraryElement library = element.getLibrary();