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

src/d8.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.
 
 
 // Defined when linking against shared lib on Windows.
 #if defined(USING_V8_SHARED) && !defined(V8_SHARED)
 #define V8_SHARED
 #endif
 
@@ skipping 329 matching lines @@
     Context::Scope context_scope(realm);
     Handle<Script> script = Shell::CompileString(
         isolate, source, name, options.compile_options, source_type);
     if (script.IsEmpty()) {
       // Print errors that happened during compilation.
       if (report_exceptions && !FLAG_debugger)
         ReportException(isolate, &try_catch);
       return false;
     }
     result = script->Run();
+    EmptyMessageQueues(isolate);
     data->realm_current_ = data->realm_switch_;
   }
   if (result.IsEmpty()) {
     DCHECK(try_catch.HasCaught());
     // Print errors that happened during execution.
     if (report_exceptions && !FLAG_debugger)
       ReportException(isolate, &try_catch);
     return false;
   }
   DCHECK(!try_catch.HasCaught());
@@ skipping 1618 matching lines @@
   }
   if (options.invoke_weak_callbacks) {
     // By sending a low memory notifications, we will try hard to collect all
     // garbage and will therefore also invoke all weak callbacks of actually
     // unreachable persistent handles.
     isolate->LowMemoryNotification();
   }
 }
 
 
+void Shell::EmptyMessageQueues(Isolate* isolate) {
+  while (v8::platform::PumpMessageLoop(g_platform, isolate)) continue;
+}
+
+
 #ifndef V8_SHARED
 bool Shell::SerializeValue(Isolate* isolate, Handle<Value> value,
                            const ObjectList& to_transfer,
                            ObjectList* seen_objects,
                            SerializationData* out_data) {
   DCHECK(out_data);
   Local<Context> context = isolate->GetCurrentContext();
 
   if (value->IsUndefined()) {
     out_data->WriteTag(kSerializationTagUndefined);
@@ skipping 441 matching lines @@
 }
 
 }  // namespace v8
 
 
 #ifndef GOOGLE3
 int main(int argc, char* argv[]) {
   return v8::Shell::Main(argc, argv);
 }
 #endif