Report promise reject with no handler (behind a flag).

src/heap/heap.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/base/bits.h"
 #include "src/base/once.h"
@@ skipping 2862 matching lines @@
   set_frozen_symbol(*factory->NewPrivateOwnSymbol());
   set_megamorphic_symbol(*factory->NewPrivateOwnSymbol());
   set_premonomorphic_symbol(*factory->NewPrivateOwnSymbol());
   set_generic_symbol(*factory->NewPrivateOwnSymbol());
   set_nonexistent_symbol(*factory->NewPrivateOwnSymbol());
   set_normal_ic_symbol(*factory->NewPrivateOwnSymbol());
   set_observed_symbol(*factory->NewPrivateOwnSymbol());
   set_stack_trace_symbol(*factory->NewPrivateOwnSymbol());
   set_uninitialized_symbol(*factory->NewPrivateOwnSymbol());
   set_home_object_symbol(*factory->NewPrivateOwnSymbol());
+  set_promise_debug_symbol(*factory->NewPrivateOwnSymbol());
 
   Handle<SeededNumberDictionary> slow_element_dictionary =
       SeededNumberDictionary::New(isolate(), 0, TENURED);
   slow_element_dictionary->set_requires_slow_elements();
   set_empty_slow_element_dictionary(*slow_element_dictionary);
 
   set_materialized_objects(*factory->NewFixedArray(0, TENURED));
 
   // Handling of script id generation is in Factory::NewScript.
   set_last_script_id(Smi::FromInt(v8::UnboundScript::kNoScriptId));
@@ skipping 3257 matching lines @@
       static_cast<int>(object_sizes_last_time_[index]));
   CODE_AGE_LIST_COMPLETE(ADJUST_LAST_TIME_OBJECT_COUNT)
 #undef ADJUST_LAST_TIME_OBJECT_COUNT
 
   MemCopy(object_counts_last_time_, object_counts_, sizeof(object_counts_));
   MemCopy(object_sizes_last_time_, object_sizes_, sizeof(object_sizes_));
   ClearObjectStats();
 }
 }
 }  // namespace v8::internal