Ignore deleted handles when processing weak roots.

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/thread.h"
@@ skipping 117 matching lines @@
   void set_raw(const Object& object) { raw_ = object.raw(); }
   static intptr_t raw_offset() { return OFFSET_OF(WeakPersistentHandle, raw_); }
   void* peer() const { return peer_; }
   void set_peer(void* peer) { peer_ = peer; }
   Dart_WeakPersistentHandleFinalizer callback() const { return callback_; }
   void set_callback(Dart_WeakPersistentHandleFinalizer callback) {
     callback_ = callback;
   }
 
   static void Finalize(WeakPersistentHandle* handle) {
-    if (handle->callback() != NULL) {
-      Dart_WeakPersistentHandleFinalizer callback = handle->callback();
+    Dart_WeakPersistentHandleFinalizer callback = handle->callback();
+    if (callback != NULL) {
       void* peer = handle->peer();
       handle->Clear();
       (*callback)(reinterpret_cast<Dart_Handle>(handle), peer);
     } else {
       handle->Clear();
     }
   }
 
  private:
   friend class WeakPersistentHandles;
@@ skipping 408 matching lines @@
           ApiNativeScope::Current()->zone()->GetBaseZone()) {}
   ApiGrowableArray()
       : BaseGrowableArray<T, ValueObject>(
           ApiNativeScope::Current()->zone()->GetBaseZone()) {}
 };
 
 
 }  // namespace dart
 
 #endif  // VM_DART_API_STATE_H_