Assert no VM handles are created in the zone that belongs to a ApiNativeScopes.

runtime/vm/dart_api_state.h

 // 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.
 
 #ifndef VM_DART_API_STATE_H_
 #define VM_DART_API_STATE_H_
 
 #include "include/dart_api.h"
 
 #include "platform/utils.h"
@@ skipping 35 matching lines @@
       OS::PrintErr("*** Starting a new Api zone 0x%" Px "(0x%" Px ")\n",
                    reinterpret_cast<intptr_t>(this),
                    reinterpret_cast<intptr_t>(&zone_));
     }
 #endif
   }
 
   // Delete all memory associated with the zone.
   ~ApiZone() {
     Isolate* isolate = Isolate::Current();
+#if defined(DEBUG)
+    if (isolate == NULL) {
+      ASSERT(zone_.handles()->CountScopedHandles() == 0);
+      ASSERT(zone_.handles()->CountZoneHandles() == 0);
+    }
+#endif
     if ((isolate != NULL) && (isolate->current_zone() == &zone_)) {
       isolate->set_current_zone(zone_.previous_);
     }
 #ifdef DEBUG
     if (FLAG_trace_zones) {
       OS::PrintErr("*** Deleting Api zone 0x%" Px "(0x%" Px ")\n",
                    reinterpret_cast<intptr_t>(this),
                    reinterpret_cast<intptr_t>(&zone_));
     }
 #endif
@@ skipping 563 matching lines @@
   ~ApiNativeScope() {
     ASSERT(Current() == this);
     OSThread::SetThreadLocal(Api::api_native_key_, 0);
   }
 
   static inline ApiNativeScope* Current() {
     return reinterpret_cast<ApiNativeScope*>(
         OSThread::GetThreadLocal(Api::api_native_key_));
   }
 
-  Zone* zone() { return zone_.GetZone(); }
+  Zone* zone() {
+    Zone* result = zone_.GetZone();
+    ASSERT(result->handles()->CountScopedHandles() == 0);
+    ASSERT(result->handles()->CountZoneHandles() == 0);
+    return result;
+  }
 
  private:
   ApiZone zone_;
 };
 
 
 // Api growable arrays use a zone for allocation. The constructor
 // picks the zone from the current isolate if in an isolate
 // environment. When outside an isolate environment it picks the zone
 // from the current native scope.
@@ skipping 330 matching lines @@
   ref->set_peer(peer);
   ref->set_callback(callback);
   // This may trigger GC, so it must be called last.
   ref->SetExternalSize(external_size, isolate);
   return ref;
 }
 
 }  // namespace dart
 
 #endif  // VM_DART_API_STATE_H_