Introduce a handle zapping setting, and enable it by default for release and debug

src/handles-inl.h

 // 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 116 matching lines @@
   v8::ImplementationUtilities::HandleScopeData* current =
       isolate->handle_scope_data();
 
   current->next = prev_next;
   current->level--;
   if (current->limit != prev_limit) {
     current->limit = prev_limit;
     DeleteExtensions(isolate);
   }
 
-#ifdef ENABLE_EXTRA_CHECKS
+#ifdef ENABLE_HANDLE_ZAPPING
   ZapRange(prev_next, prev_limit);
 #endif
 }
 
 
 template <typename T>
 Handle<T> HandleScope::CloseAndEscape(Handle<T> handle_value) {
   v8::ImplementationUtilities::HandleScopeData* current =
       isolate_->handle_scope_data();
 
@@ skipping 55 matching lines @@
   current->level = level_;
   ASSERT_EQ(current->next, current->limit);
   current->limit = limit_;
 }
 
 #endif
 
 } }  // namespace v8::internal
 
 #endif  // V8_HANDLES_INL_H_