Implement operator-is for interfaces' supertypes and String's supertypes. Also, improve stack trace…

dart/frog/leg/resolver.dart

Index: dart/frog/leg/resolver.dart
diff --git a/dart/frog/leg/resolver.dart b/dart/frog/leg/resolver.dart
index c3fce80e209e5f3b5f5707b573d1766a0c834f92..502a013a839d25d4388504d35df67a28e79dfab1 100644
--- a/dart/frog/leg/resolver.dart
+++ b/dart/frog/leg/resolver.dart
@@ -263,6 +263,7 @@ class ResolverTask extends CompilerTask {
         Link<Type> interfaceSupertypes =
             getOrCalculateAllSupertypes(element, seen);
         supertypes = supertypes.reversePrependAll(interfaceSupertypes);
+        supertypes = supertypes.prepend(interfaces.head);
       }
       seen.remove(classElement);
       classElement.allSupertypes = supertypes;