Introduce v8::MicrotasksScope.

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index a6f73128882581fcda0dc2ee417996ac40cb9072..a784619d6fb3a4be19baff4da3389ed40fe9caff 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -2710,7 +2710,11 @@ void Isolate::RemoveCallCompletedCallback(CallCompletedCallback callback) {
 
 void Isolate::FireCallCompletedCallback() {
   bool has_call_completed_callbacks = !call_completed_callbacks_.is_empty();
-  bool run_microtasks = autorun_microtasks() && pending_microtask_count();
+  bool run_microtasks =
+      pending_microtask_count() &&
+      !handle_scope_implementer()->HasMicrotasksSuppressions() &&
+      handle_scope_implementer()->microtasks_policy() ==
+          v8::MicrotasksPolicy::kAuto;
   if (!has_call_completed_callbacks && !run_microtasks) return;
 
   if (!handle_scope_implementer()->CallDepthIsZero()) return;