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 747dc384155f431317e44ebd8ef62a5211924c10..ea79c41bb8a7e08acdd4d4eb812ae6b76af5b4c1 100644
--- a/pkg/compiler/lib/src/compiler.dart
+++ b/pkg/compiler/lib/src/compiler.dart
@@ -1175,7 +1175,9 @@ 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;
     }