Reduce usage of .enclosingElement to get enclosing class.

lib/compiler/implementation/enqueue.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.
 
 class EnqueueTask extends CompilerTask {
   final Enqueuer codegen;
   final Enqueuer resolution;
 
   String get name() => 'Enqueue';
 
@@ skipping 62 matching lines @@
 
   void addToWorkList(Element element, [TreeElements elements]) {
     if (element.isForeign()) return;
     if (compiler.phase == Compiler.PHASE_RECOMPILING) return;
     if (queueIsClosed) {
       if (isResolutionQueue && getCachedElements(element) !== null) return;
       compiler.internalErrorOnElement(element, "Work list is closed.");
     }
     if (!isResolutionQueue &&
         element.kind === ElementKind.GENERATIVE_CONSTRUCTOR) {
-      registerInstantiatedClass(element.enclosingElement);
+      registerInstantiatedClass(element.getEnclosingClass());
     }
     if (elements === null) {
       elements = getCachedElements(element);
     }
     queue.add(new WorkItem(element, elements));
   }
 
   bool canBeRecompiled(Element element) {
     // Only member functions can be recompiled. An exception to this is members
     // of closures. They are processed as part of the enclosing function and not
@@ skipping 220 matching lines @@
   void registerIsCheck(Element element) {
     universe.isChecks.add(element);
   }
 
   void forEach(f(WorkItem work)) {
     while (!queue.isEmpty()) {
       f(queue.removeLast());
     }
   }
 }