Revert "Remove Registry from registerMetadataConstant" and "Serialize metadata"

pkg/compiler/lib/src/types/constants.dart

Index: pkg/compiler/lib/src/types/constants.dart
diff --git a/pkg/compiler/lib/src/types/constants.dart b/pkg/compiler/lib/src/types/constants.dart
index d66a31c3b6f1b185e1ab01e3cfd5a4c7cc08f11c..a3b2faa917f308e56224fd7a85be2d8a7e7e743a 100644
--- a/pkg/compiler/lib/src/types/constants.dart
+++ b/pkg/compiler/lib/src/types/constants.dart
@@ -105,11 +105,6 @@ class ConstantValueTypeMasks extends ConstantValueVisitor<TypeMask, Compiler> {
   }
 
   @override
-  TypeMask visitNonConstant(NonConstantValue constant, Compiler compiler) {
-    return compiler.typesTask.nullType;
-  }
-
-  @override
   TypeMask visitString(StringConstantValue constant, Compiler compiler) {
     return compiler.typesTask.stringType;
   }