Add a check that weak object handle is not in NEAR_DEATH state after weak callback invocation.

test/cctest/test-mark-compact.cc

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 255 matching lines @@
 
   CHECK(Heap::CollectGarbage(0, OLD_POINTER_SPACE));
   CHECK_EQ(1, gc_starts);
   CHECK_EQ(gc_ends, gc_starts);
 }
 
 
 static int NumberOfWeakCalls = 0;
 static void WeakPointerCallback(v8::Persistent<v8::Value> handle, void* id) {
   NumberOfWeakCalls++;
+  handle.Dispose();
 }
 
 TEST(ObjectGroups) {
   InitializeVM();
 
   NumberOfWeakCalls = 0;
   v8::HandleScope handle_scope;
 
   Handle<Object> g1s1 =
     GlobalHandles::Create(Heap::AllocateFixedArray(1));
@@ skipping 46 matching lines @@
     Object** g2_objects[] = { g2s1.location(), g2s2.location() };
     GlobalHandles::AddGroup(g1_objects, 2);
     GlobalHandles::AddGroup(g2_objects, 2);
   }
 
   CHECK(Heap::CollectGarbage(0, OLD_POINTER_SPACE));
 
   // All objects should be gone. 5 global handles in total.
   CHECK_EQ(5, NumberOfWeakCalls);
 }