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

src/execution.h

 // Copyright 2014 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.
 
 #ifndef V8_EXECUTION_H_
 #define V8_EXECUTION_H_
 
 #include "src/handles.h"
 
 namespace v8 {
@@ skipping 67 matching lines @@
       Isolate* isolate, Handle<Object> obj);
 
   // ECMA-262 9.9
   MUST_USE_RESULT static MaybeHandle<Object> ToObject(
       Isolate* isolate, Handle<Object> obj);
 
   // Create a new date object from 'time'.
   MUST_USE_RESULT static MaybeHandle<Object> NewDate(
       Isolate* isolate, double time);
 
+  MUST_USE_RESULT static MaybeHandle<Object> PromiseHasRejectHandler(
+      Isolate* isolate, Handle<Object> promise);
+
   // Create a new regular expression object from 'pattern' and 'flags'.
   MUST_USE_RESULT static MaybeHandle<JSRegExp> NewJSRegExp(
       Handle<String> pattern, Handle<String> flags);
 
   // Used to implement [] notation on strings (calls JS code)
   static Handle<Object> CharAt(Handle<String> str, uint32_t index);
 
   static Handle<Object> GetFunctionFor();
   MUST_USE_RESULT static MaybeHandle<JSFunction> InstantiateFunction(
       Handle<FunctionTemplateInfo> data);
@@ skipping 171 matching lines @@
   friend class Isolate;
   friend class StackLimitCheck;
   friend class PostponeInterruptsScope;
 
   DISALLOW_COPY_AND_ASSIGN(StackGuard);
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_EXECUTION_H_