[promisehook] Implement PromiseHook

src/promise-utils.cc

 // Copyright 2016 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/promise-utils.h"
 
 #include "src/factory.h"
 #include "src/isolate.h"
 #include "src/objects-inl.h"
 
 namespace v8 {
 namespace internal {
 
-JSObject* PromiseUtils::GetPromise(Handle<Context> context) {
-  return JSObject::cast(context->get(kPromiseSlot));
+JSPromise* PromiseUtils::GetPromise(Handle<Context> context) {
+  return JSPromise::cast(context->get(kPromiseSlot));
 }
 
 Object* PromiseUtils::GetDebugEvent(Handle<Context> context) {
   return context->get(kDebugEventSlot);
 }
 
 bool PromiseUtils::HasAlreadyVisited(Handle<Context> context) {
   return Smi::cast(context->get(kAlreadyVisitedSlot))->value() != 0;
 }
 
@@ skipping 33 matching lines @@
 
   resolve_fun->set_context(*context);
   reject_fun->set_context(*context);
 
   *resolve = resolve_fun;
   *reject = reject_fun;
 }
 
 }  // namespace internal
 }  // namespace v8