[promises] cleanup default promise handlers

src/objects.h

 // Copyright 2015 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_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 #include <memory>
 
@@ skipping 8489 matching lines @@
 
 class JSPromise : public JSObject {
  public:
   DECL_INT_ACCESSORS(status)
   DECL_ACCESSORS(result, Object)
 
   // There are 3 possible states for these fields --
   // 1) Undefined -- This is the zero state when there is no callback
   // or deferred fields registered.
   //
-  // 2) Object -- There is a single Callable directly attached to the
+  // 2) Object -- There is a single callback directly attached to the
   // fulfill_reactions, reject_reactions and the deferred fields are
   // directly attached to the slots. In this state, deferred_promise
   // is a JSReceiver and deferred_on_{resolve, reject} are Callables.
   //
   // 3) FixedArray -- There is more than one callback and deferred
   // fields attached to a FixedArray.
+  //
+  // The callback can be a Callable or a Symbol.
   DECL_ACCESSORS(deferred_promise, Object)
   DECL_ACCESSORS(deferred_on_resolve, Object)
   DECL_ACCESSORS(deferred_on_reject, Object)
   DECL_ACCESSORS(fulfill_reactions, Object)
   DECL_ACCESSORS(reject_reactions, Object)
 
   DECL_INT_ACCESSORS(flags)
 
   // [has_handler]: Whether this promise has a reject handler or not.
   DECL_BOOLEAN_ACCESSORS(has_handler)
@@ skipping 3109 matching lines @@
   }
 };
 
 
 }  // NOLINT, false-positive due to second-order macros.
 }  // NOLINT, false-positive due to second-order macros.
 
 #include "src/objects/object-macros-undef.h"
 
 #endif  // V8_OBJECTS_H_