Extract ResolutionWorldBuilderBase from ElementResolutionWorldBuilder

pkg/compiler/lib/src/resolution/resolution.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.
 
 library dart2js.resolution;
 
 import 'dart:collection' show Queue;
 
 import '../common.dart';
 import '../common/names.dart' show Identifiers;
@@ skipping 252 matching lines @@
 
       // Get the resolution tree and check that the resolved
       // function doesn't use 'super' if it is mixed into another
       // class. This is the part of the 'super' mixin check that
       // happens when a function is resolved after the mixin
       // application has been performed.
       TreeElements resolutionTree = registry.mapping;
       ClassElement enclosingClass = element.enclosingClass;
       if (enclosingClass != null) {
         // TODO(johnniwinther): Find another way to obtain mixin uses.
-        Iterable<MixinApplicationElement> mixinUses =
-            world.allMixinUsesOf(enclosingClass);
         ClassElement mixin = enclosingClass;
-        for (MixinApplicationElement mixinApplication in mixinUses) {
+        for (MixinApplicationElement mixinApplication
+            in world.allMixinUsesOf(enclosingClass)) {
           checkMixinSuperUses(resolutionTree, mixinApplication, mixin);
         }
       }
 
       // TODO(9631): support noSuchMethod on native classes.
       if (element.isFunction &&
           element.isInstanceMember &&
           element.name == Identifiers.noSuchMethod_ &&
           _isNativeClassOrExtendsNativeClass(enclosingClass)) {
         reporter.reportErrorMessage(tree, MessageKind.NO_SUCH_METHOD_IN_NATIVE);
@@ skipping 857 matching lines @@
   TreeElements get treeElements {
     assert(invariant(this, _treeElements != null,
         message: "TreeElements have not been computed for $this."));
     return _treeElements;
   }
 
   void reuseElement() {
     _treeElements = null;
   }
 }