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

lib/compiler/implementation/lib/interceptors.dart

Index: lib/compiler/implementation/lib/interceptors.dart
diff --git a/lib/compiler/implementation/lib/interceptors.dart b/lib/compiler/implementation/lib/interceptors.dart
index 17f8e51fa7534f2f73ef37a3575a80029513cf7a..64415a19d1e1c2ec25d01ec9fe184afade15c442 100644
--- a/lib/compiler/implementation/lib/interceptors.dart
+++ b/lib/compiler/implementation/lib/interceptors.dart
@@ -640,3 +640,17 @@ isOdd(receiver) {
 }
 
 get$toString(receiver) => () => toString(receiver);
+
+runtimeType(receiver) {
+  if (receiver is int) {
+    return getOrCreateCachedRuntimeType('int');
+  } else if (receiver is String) {
+    return getOrCreateCachedRuntimeType('String');
+  } else if (receiver is double) {
+    return getOrCreateCachedRuntimeType('double');
+  } else if (receiver is List) {
+    return getOrCreateCachedRuntimeType('List');
+  } else {
+    return UNINTERCEPTED(receiver.runtimeType());
+  }
+}