Introduce BackendImpact to separate enqueueing from data.

pkg/compiler/lib/src/resolution/registry.dart

Index: pkg/compiler/lib/src/resolution/registry.dart
diff --git a/pkg/compiler/lib/src/resolution/registry.dart b/pkg/compiler/lib/src/resolution/registry.dart
index 51aa37c4250bc8f48dd5b956d449e5505b10d7b0..4b6bc54d53797e7ad9df0a87de5aed066d60797c 100644
--- a/pkg/compiler/lib/src/resolution/registry.dart
+++ b/pkg/compiler/lib/src/resolution/registry.dart
@@ -668,10 +668,6 @@ class ResolutionRegistry implements Registry {
     worldImpact.registerFeature(Feature.ABSTRACT_CLASS_INSTANTIATION);
   }
 
-  void registerNewSymbol() {
-    worldImpact.registerFeature(Feature.NEW_SYMBOL);
-  }
-
   void registerRequiredType(DartType type, Element enclosingElement) {
     worldImpact.registerRequiredType(type);
     mapping.addRequiredType(type);