Fix incorrect assertion failures in noopt regarding removing classes that still have constants.

runtime/vm/heap.cc

 // 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.
 
 #include "vm/heap.h"
 
 #include "platform/assert.h"
 #include "platform/utils.h"
 #include "vm/flags.h"
 #include "vm/isolate.h"
@@ skipping 428 matching lines @@
 }
 
 
 void Heap::CollectAllGarbage() {
   Thread* thread = Thread::Current();
   CollectNewSpaceGarbage(thread, kInvokeApiCallbacks, kFull);
   CollectOldSpaceGarbage(thread, kInvokeApiCallbacks, kFull);
 }
 
 
+#if defined(DEBUG)
+void Heap::WaitForSweeperTasks() {
+  Thread* thread = Thread::Current();
+  {
+    MonitorLocker ml(old_space_.tasks_lock());
+    while (old_space_.tasks() > 0) {
+      ml.WaitWithSafepointCheck(thread);
+    }
+  }
+}
+#endif
+
+
 bool Heap::ShouldPretenure(intptr_t class_id) const {
   if (class_id == kOneByteStringCid) {
     return pretenure_policy_ > 0;
   } else {
     return false;
   }
 }
 
 
 void Heap::UpdatePretenurePolicy() {
@@ skipping 382 matching lines @@
   Dart::vm_isolate()->heap()->WriteProtect(false, include_code_pages_);
 }
 
 
 WritableVMIsolateScope::~WritableVMIsolateScope() {
   ASSERT(Dart::vm_isolate()->heap()->UsedInWords(Heap::kNew) == 0);
   Dart::vm_isolate()->heap()->WriteProtect(true, include_code_pages_);
 }
 
 }  // namespace dart