Avoid generating is$Object, and fix a typo in a condition.

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 246 matching lines @@
         }
         if (isResolutionQueue) {
           compiler.resolver.checkMembers(cls);
         }
 
         if (compiler.enableTypeAssertions) {
           // We need to register is checks and helpers for checking
           // assignments to fields.
           // TODO(ngeoffray): This should really move to the backend.
           cls.localMembers.forEach((Element member) {
-            if (!member.isInstanceMember() && !member.isField()) return;
+            if (!member.isInstanceMember() || !member.isField()) return;
             DartType type = member.computeType(compiler);
             registerIsCheck(type);
             SourceString helper = compiler.backend.getCheckedModeHelper(type);
             if (helper != null) {
               Element helperElement = compiler.findHelper(helper);
               registerStaticUse(helperElement);
             }
           });
         }
       }
@@ skipping 115 matching lines @@
   }
 
   void forEach(f(WorkItem work)) {
     while (!queue.isEmpty()) {
       f(queue.removeLast()); // TODO(kasperl): Why isn't this removeFirst?
     }
   }
 
   String toString() => 'Enqueuer($name)';
 }