Revert "Remove WorldImpact from caches when no longer needed."

pkg/compiler/lib/src/enqueue.dart

Index: pkg/compiler/lib/src/enqueue.dart
diff --git a/pkg/compiler/lib/src/enqueue.dart b/pkg/compiler/lib/src/enqueue.dart
index 3744f2dca440c95223549e6146cb792218090bff..53796dc0280bd5b91654605cabf17610745d66ce 100644
--- a/pkg/compiler/lib/src/enqueue.dart
+++ b/pkg/compiler/lib/src/enqueue.dart
@@ -58,9 +58,7 @@ import 'universe/use.dart' show
     TypeUse,
     TypeUseKind;
 import 'universe/world_impact.dart' show
-    ImpactUseCase,
-    WorldImpact,
-    WorldImpactVisitor;
+    WorldImpact;
 import 'util/util.dart' show
     Link,
     Setlet;
@@ -119,14 +117,10 @@ abstract class Enqueuer {
   bool hasEnqueuedReflectiveElements = false;
   bool hasEnqueuedReflectiveStaticFields = false;
 
-  WorldImpactVisitor impactVisitor;
-
   Enqueuer(this.name,
            this.compiler,
            this.itemCompilationContextCreator,
-           this.strategy) {
-    impactVisitor = new _EnqueuerImpactVisitor(this);
-  }
+           this.strategy);
 
   // TODO(johnniwinther): Move this to [ResolutionEnqueuer].
   Resolution get resolution => compiler.resolution;
@@ -148,8 +142,6 @@ abstract class Enqueuer {
 
   Iterable<ClassElement> get processedClasses => _processedClasses;
 
-  ImpactUseCase get impactUse;
-
   /**
    * Documentation wanted -- johnniwinther
    *
@@ -174,8 +166,10 @@ abstract class Enqueuer {
 
   /// Apply the [worldImpact] of processing [element] to this enqueuer.
   void applyImpact(Element element, WorldImpact worldImpact) {
-    compiler.impactStrategy.visitImpact(
-        element, worldImpact, impactVisitor, impactUse);
+    // TODO(johnniwinther): Optimize the application of the world impact.
+    worldImpact.dynamicUses.forEach(registerDynamicUse);
+    worldImpact.staticUses.forEach(registerStaticUse);
+    worldImpact.typeUses.forEach(registerTypeUse);
   }
 
   void registerInstantiatedType(InterfaceType type,
@@ -747,10 +741,6 @@ class ResolutionEnqueuer extends Enqueuer {
    */
   final Queue<DeferredTask> deferredTaskQueue;
 
-  static const ImpactUseCase IMPACT_USE = const ImpactUseCase('ResolutionEnqueuer');
-
-  ImpactUseCase get impactUse => IMPACT_USE;
-
   ResolutionEnqueuer(Compiler compiler,
                      ItemCompilationContext itemCompilationContextCreator(),
                      EnqueuerStrategy strategy)
@@ -906,10 +896,6 @@ class CodegenEnqueuer extends Enqueuer {
 
   bool enabledNoSuchMethod = false;
 
-  static const ImpactUseCase IMPACT_USE = const ImpactUseCase('CodegenEnqueuer');
-
-  ImpactUseCase get impactUse => IMPACT_USE;
-
   CodegenEnqueuer(Compiler compiler,
                   ItemCompilationContext itemCompilationContextCreator(),
                   EnqueuerStrategy strategy)
@@ -1053,24 +1039,3 @@ class TreeShakingEnqueuerStrategy implements EnqueuerStrategy {
     enqueuer.handleUnseenSelectorInternal(dynamicUse);
   }
 }
-
-class _EnqueuerImpactVisitor implements WorldImpactVisitor {
-  final Enqueuer enqueuer;
-
-  _EnqueuerImpactVisitor(this.enqueuer);
-
-  @override
-  void visitDynamicUse(DynamicUse dynamicUse) {
-    enqueuer.registerDynamicUse(dynamicUse);
-  }
-
-  @override
-  void visitStaticUse(StaticUse staticUse) {
-    enqueuer.registerStaticUse(staticUse);
-  }
-
-  @override
-  void visitTypeUse(TypeUse typeUse) {
-    enqueuer.registerTypeUse(typeUse);
-  }
-}