Avoid eager enqueueing from resolution

pkg/compiler/lib/src/common/backend_api.dart

Index: pkg/compiler/lib/src/common/backend_api.dart
diff --git a/pkg/compiler/lib/src/common/backend_api.dart b/pkg/compiler/lib/src/common/backend_api.dart
index b4425f5a33c4836764956478cdabb55aeaae3731..948fdbaaa35ba37c67d042b082d40b484bec309b 100644
--- a/pkg/compiler/lib/src/common/backend_api.dart
+++ b/pkg/compiler/lib/src/common/backend_api.dart
@@ -227,7 +227,7 @@ abstract class Backend {
   /// Call this method to enable support for isolates.
   void enableIsolateSupport(Enqueuer enqueuer) {}
 
-  void registerRequiredType(DartType type, Element enclosingElement) {}
+  void registerRequiredType(DartType type) {}
 
   void registerConstSymbol(String name, Registry registry) {}
   void registerNewSymbol(Registry registry) {}
@@ -401,4 +401,4 @@ abstract class ForeignResolver {
 
   /// Resolves [typeName] to a type in the context of [node].
   DartType resolveTypeFromString(Node node, String typeName);
-}
+}