Optimize subclass/subtype queries

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

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of js_backend;
 
 const VERBOSE_OPTIMIZER_HINTS = false;
 
 class JavaScriptItemCompilationContext extends ItemCompilationContext {
   final Set<HInstruction> boundsChecked = new Set<HInstruction>();
@@ skipping 956 matching lines @@
       }
       return result;
     });
   }
 
   Set<ClassElement> nativeSubclassesOfMixin(ClassElement mixin) {
     ClassWorld classWorld = compiler.world;
     Iterable<MixinApplicationElement> uses = classWorld.mixinUsesOf(mixin);
     Set<ClassElement> result = null;
     for (MixinApplicationElement use in uses) {
-      Iterable<ClassElement> subclasses = classWorld.strictSubclassesOf(use);
-      for (ClassElement subclass in subclasses) {
+      classWorld.forEachStrictSubclassOf(use, (ClassElement subclass) {
         if (isNativeOrExtendsNative(subclass)) {
           if (result == null) result = new Set<ClassElement>();
           result.add(subclass);
         }
-      }
+      });
     }
     return result;
   }
 
   bool operatorEqHandlesNullArgument(FunctionElement operatorEqfunction) {
     return specialOperatorEqClasses.contains(
         operatorEqfunction.enclosingClass);
   }
 
   void validateInterceptorImplementsAllObjectMethods(
@@ skipping 1195 matching lines @@
         });
         // 3) all members, including fields via getter/setters (if resolved)
         cls.forEachClassMember((Member member) {
           if (resolution.hasBeenProcessed(member.element)) {
             memberNames.add(member.name);
             reflectableMembers.add(member.element);
           }
         });
         // 4) all overriding members of subclasses/subtypes (should be resolved)
         if (compiler.world.hasAnyStrictSubtype(cls)) {
-          for (ClassElement subcls in compiler.world.strictSubtypesOf(cls)) {
+          compiler.world.forEachStrictSubtypeOf(cls, (ClassElement subcls) {
             subcls.forEachClassMember((Member member) {
               if (memberNames.contains(member.name)) {
                 // TODO(20993): find out why this assertion fails.
                 // assert(invariant(member.element,
                 //    resolution.hasBeenProcessed(member.element)));
                 if (resolution.hasBeenProcessed(member.element)) {
                   reflectableMembers.add(member.element);
                 }
               }
             });
-          }
+          });
         }
         // 5) all its closures
         List<LocalFunctionElement> closures = closureMap[cls];
         if (closures != null) {
           reflectableMembers.addAll(closures);
           foundClosure = true;
         }
       } else {
         // check members themselves
         cls.constructors.forEach((ConstructorElement element) {
@@ skipping 948 matching lines @@
     }
   }
 
   @override
   void onImpactUsed(ImpactUseCase impactUse) {
     if (impactUse == DeferredLoadTask.IMPACT_USE) {
       resolution.emptyCache();
     }
   }
 }