Let the second pass phantom callbacks run in a separate task on the foreground thread.

src/d8.h

 // 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.
 
 #ifndef V8_D8_H_
 #define V8_D8_H_
 
 #ifndef V8_SHARED
 #include "src/allocation.h"
 #include "src/hashmap.h"
@@ skipping 331 matching lines @@
                             SourceType source_type = SCRIPT);
   static const char* ToCString(const v8::String::Utf8Value& value);
   static void ReportException(Isolate* isolate, TryCatch* try_catch);
   static Handle<String> ReadFile(Isolate* isolate, const char* name);
   static Local<Context> CreateEvaluationContext(Isolate* isolate);
   static int RunMain(Isolate* isolate, int argc, char* argv[]);
   static int Main(int argc, char* argv[]);
   static void Exit(int exit_code);
   static void OnExit(Isolate* isolate);
   static void CollectGarbage(Isolate* isolate);
+  static void EmptyMessageQueues(Isolate* isolate);
 
 #ifndef V8_SHARED
   // TODO(binji): stupid implementation for now. Is there an easy way to hash an
   // object for use in i::HashMap? By pointer?
   typedef i::List<Handle<Object>> ObjectList;
   static bool SerializeValue(Isolate* isolate, Handle<Value> value,
                              const ObjectList& to_transfer,
                              ObjectList* seen_objects,
                              SerializationData* out_data);
   static MaybeLocal<Value> DeserializeValue(Isolate* isolate,
@@ skipping 115 matching lines @@
   static void RunShell(Isolate* isolate);
   static bool SetOptions(int argc, char* argv[]);
   static Handle<ObjectTemplate> CreateGlobalTemplate(Isolate* isolate);
 };
 
 
 }  // namespace v8
 
 
 #endif  // V8_D8_H_