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 9d374415812fa5186686f1a06696c320f382030c..49e566299221f1896f4792beb3ac7589ef3d3534 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);
+  }
 }