Handle symbol literals in closed_world2_test

pkg/compiler/lib/src/inferrer/builder.dart

Index: pkg/compiler/lib/src/inferrer/builder.dart
diff --git a/pkg/compiler/lib/src/inferrer/builder.dart b/pkg/compiler/lib/src/inferrer/builder.dart
index f5abd99a7c94b0abb1a57870cd123d551ffaea28..8ac2d4a99e54834036fc7907dd4d3d5fd58f9ecb 100644
--- a/pkg/compiler/lib/src/inferrer/builder.dart
+++ b/pkg/compiler/lib/src/inferrer/builder.dart
@@ -242,7 +242,8 @@ class ElementGraphBuilder extends ast.Visitor<TypeInformation>
     // TODO(kasperl): We should be able to tell that the type of a literal
     // symbol is always a non-null exact symbol implementation -- not just
     // any non-null subtype of the symbol interface.
-    return types.nonNullSubtype(closedWorld.commonElements.symbolClass);
+    return types
+        .nonNullSubtype(closedWorld.commonElements.symbolImplementationClass);
   }
 
   @override