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

lib/compiler/implementation/lib/core_patch.dart

Index: lib/compiler/implementation/lib/core_patch.dart
diff --git a/lib/compiler/implementation/lib/core_patch.dart b/lib/compiler/implementation/lib/core_patch.dart
index 5aa14c12e83825c75bb691f0e802f53041876aaf..93b9ea15fb3c89f5d24f891ad2320a9767f34f61 100644
--- a/lib/compiler/implementation/lib/core_patch.dart
+++ b/lib/compiler/implementation/lib/core_patch.dart
@@ -23,6 +23,11 @@ patch class Object {
   patch void noSuchMethod(String name, List args) {
     throw new NoSuchMethodError(this, name, args);
   }
+
+  patch Type runtimeType() {
+    String key = getRuntimeTypeString(this);
+    return getOrCreateCachedRuntimeType(key);
+  }
 }