Remove Enqueuer argument from Backend.registerStaticUse

pkg/compiler/lib/src/js_backend/type_variable_handler.dart

Index: pkg/compiler/lib/src/js_backend/type_variable_handler.dart
diff --git a/pkg/compiler/lib/src/js_backend/type_variable_handler.dart b/pkg/compiler/lib/src/js_backend/type_variable_handler.dart
index d7c3281f056ff48349ad0bc3dfd0a8d450816848..595da954243379ce6dc6ad47bcb2554fcb369cbe 100644
--- a/pkg/compiler/lib/src/js_backend/type_variable_handler.dart
+++ b/pkg/compiler/lib/src/js_backend/type_variable_handler.dart
@@ -57,10 +57,11 @@ class TypeVariableHandler {
   JavaScriptBackend get _backend => _compiler.backend;
   DiagnosticReporter get reporter => _compiler.reporter;
 
-  void onQueueEmpty(Enqueuer enqueuer) {
-    if (enqueuer.isResolutionQueue) return;
-
-    enqueuer.applyImpact(null, impactBuilder.flush());
+  /// Compute the [WorldImpact] for the type variables registered since last
+  /// flush.
+  WorldImpact flush({bool forResolution}) {
+    if (forResolution) return const WorldImpact();
+    return impactBuilder.flush();
   }
 
   void registerClassWithTypeVariables(