Resolution for issue #5092: Unit test handle checks consider dangling handles to be valid.

runtime/vm/thread_registry.cc

 // Copyright (c) 2015, 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/thread_registry.h"
 
 #include "vm/isolate.h"
 #include "vm/json_stream.h"
 #include "vm/lockers.h"
 
@@ skipping 87 matching lines @@
   JSONArray threads(stream);
   Thread* current = active_list_;
   while (current != NULL) {
     threads.AddValue(current);
     current = current->next_;
   }
 }
 #endif
 
 
+bool ThreadRegistry::IsValidHandle(Dart_Handle handle) const {
+  MonitorLocker ml(threads_lock());
+  Thread* current = active_list_;
+  while (current != NULL) {
+    if (current->IsValidHandle(handle)) {
+      return true;
+    }
+    current = current->next_;
+  }
+  return false;
+}
+
+
 intptr_t ThreadRegistry::CountZoneHandles() const {
   MonitorLocker ml(threads_lock());
   intptr_t count = 0;
   Thread* current = active_list_;
   while (current != NULL) {
     count += current->CountZoneHandles();
     current = current->next_;
   }
   return count;
 }
@@ skipping 70 matching lines @@
   uintptr_t memory_high_watermarks_total = 0;
   Thread* current = active_list_;
   while (current != NULL) {
     memory_high_watermarks_total += current->memory_high_watermark();
     current = current->next_;
   }
   return memory_high_watermarks_total;
 }
 
 }  // namespace dart