Fix a performance regressions introduced by r10632.

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 151 matching lines @@
                 selector.namedArguments);
             registerDynamicInvocation(compiler.namer.CLOSURE_INVOCATION_NAME,
                                       call);
           }
         }
       }
     });
   }
 
   void processInstantiatedClassMember(Element member) {
+    if (member.isConstructor()) return;
     if (universe.generatedCode.containsKey(member)) return;
     if (resolvedElements[member] !== null) return;
 
     if (!member.isInstanceMember()) return;
     if (member.isField()) return;
 
     String memberName = member.name.slowToString();
     Link<Element> members = instanceMembersByName.putIfAbsent(
         memberName, () => const EmptyLink<Element>());
     instanceMembersByName[memberName] = members.prepend(member);
@@ skipping 168 matching lines @@
   void forEach(f(WorkItem work)) {
     while (!queue.isEmpty()) {
       do {
         f(queue.removeLast());
       } while (!queue.isEmpty());
       // TODO(ahe): we shouldn't register the field closure invocations here.
       registerFieldClosureInvocations();
     }
   }
 }