Move microtask queueing logic from JavaScript to C++

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index b559015cf8d2594cfd918ea5b03e7f9532915414..7d4ea166396175cf496e694978153abe8397e5e6 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -6626,16 +6626,13 @@ void Isolate::RemoveCallCompletedCallback(CallCompletedCallback callback) {
 
 
 void Isolate::RunMicrotasks() {
-  i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(this);
-  i::HandleScope scope(i_isolate);
-  i_isolate->RunMicrotasks();
+  reinterpret_cast<i::Isolate*>(this)->RunMicrotasks();
 }
 
 
 void Isolate::EnqueueMicrotask(Handle<Function> microtask) {
-  i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(this);
-  ENTER_V8(i_isolate);
-  i::Execution::EnqueueMicrotask(i_isolate, Utils::OpenHandle(*microtask));
+  i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
+  isolate->EnqueueMicrotask(Utils::OpenHandle(*microtask));
 }