Enqueue superclasses instead of supertypes.

pkg/compiler/lib/src/compiler.dart

Index: pkg/compiler/lib/src/compiler.dart
diff --git a/pkg/compiler/lib/src/compiler.dart b/pkg/compiler/lib/src/compiler.dart
index 0ccc51ae8d132fa41d54e278714fc11cb4fcc755..83d1a7c097d666973e5352a5b04d2f97e4548471 100644
--- a/pkg/compiler/lib/src/compiler.dart
+++ b/pkg/compiler/lib/src/compiler.dart
@@ -1177,7 +1177,9 @@ abstract class Compiler implements DiagnosticListener {
         // code is artificially used.
         // If compilation failed, it is possible that the error prevents the
         // compiler from analyzing all the code.
-        reportUnusedCode();
+        // TODO(johnniwinther): Reenable this when the reporting is more
+        // precise.
+        //reportUnusedCode();
       }
       return;
     }