Put zapping of local handles behind the extra checks flag.

src/apiutils.h

 // Copyright 2012 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 49 matching lines @@
     ASSERT(implicit_args[v8::Arguments::kHolderIndex]->IsHeapObject());
     // The implicit isolate argument is not tagged and looks like a SMI.
     ASSERT(implicit_args[v8::Arguments::kIsolateIndex]->IsSmi());
 
     return v8::Arguments(implicit_args, argv, argc, is_construct_call);
   }
 
   // Introduce an alias for the handle scope data to allow non-friends
   // to access the HandleScope data.
   typedef v8::HandleScope::Data HandleScopeData;
-
-#ifdef DEBUG
-  static void ZapHandleRange(internal::Object** begin, internal::Object** end);
-#endif
 };
 
 }  // namespace v8
 
 #endif  // V8_APIUTILS_H_