Provide API support for weak handles and post-mortem finalization.

runtime/vm/handles_impl.h

 // Copyright (c) 2011, 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_HANDLES_IMPL_H_
 #define VM_HANDLES_IMPL_H_
 
 namespace dart {
 
 DECLARE_DEBUG_FLAG(bool, trace_handles_count);
@@ skipping 285 matching lines @@
   }
 }
 
 
 template <int kHandleSizeInWords, int kHandlesPerChunk, int kOffsetOfRawPtr>
 void Handles<kHandleSizeInWords,
              kHandlesPerChunk,
              kOffsetOfRawPtr>::HandlesBlock::Visit(HandleVisitor* visitor) {
   ASSERT(visitor != NULL);
   for (intptr_t i = 0; i < next_handle_slot_; i += kHandleSizeInWords) {
-    visitor->Visit(&data_[i + kOffsetOfRawPtr/kWordSize]);
+    visitor->VisitHandle(reinterpret_cast<uword>(&data_[i]));
   }
 }
 
 
 #if defined(DEBUG)
 template <int kHandleSizeInWords, int kHandlesPerChunk, int kOffsetOfRawPtr>
 void Handles<kHandleSizeInWords,
              kHandlesPerChunk,
              kOffsetOfRawPtr>::HandlesBlock::ZapFreeHandles() {
   // Reinitialize the handle area to some uninitialized value.
   for (intptr_t i = next_handle_slot_;
        i < (kHandleSizeInWords * kHandlesPerChunk);
        i++) {
     data_[i] = kZapUninitializedWord;
   }
 }
 #endif
 
 
 template <int kHandleSizeInWords, int kHandlesPerChunk, int kOffsetOfRawPtr>
 int Handles<kHandleSizeInWords,
             kHandlesPerChunk,
             kOffsetOfRawPtr>::HandlesBlock::HandleCount() const {
   return (next_handle_slot_ / kHandleSizeInWords);
 }
 
 }  // namespace dart
 
 #endif  // VM_HANDLES_IMPL_H_