Introduce debug events for Microtask queue.

src/debug.cc

Index: src/debug.cc
diff --git a/src/debug.cc b/src/debug.cc
index 94fdb47e33d39ca68b08fef5e3aa47f2e52636d3..f83d9373f990e65e22555f9b1123a8946afec46e 100644
--- a/src/debug.cc
+++ b/src/debug.cc
@@ -2551,6 +2551,13 @@ MaybeHandle<Object> Debug::MakePromiseEvent(Handle<JSObject> event_data) {
 }
 
 
+MaybeHandle<Object> Debug::MakeAsyncTaskEvent(Handle<JSObject> task_event) {
+  // Create the async task event object.
+  Handle<Object> argv[] = { task_event };
+  return MakeJSObject("MakeAsyncTaskEvent", ARRAY_SIZE(argv), argv);
+}
+
+
 void Debug::OnException(Handle<Object> exception, bool uncaught) {
   if (in_debug_scope() || ignore_events()) return;
 
@@ -2715,6 +2722,25 @@ void Debug::OnPromiseEvent(Handle<JSObject> data) {
 }
 
 
+void Debug::OnAsyncTaskEvent(Handle<JSObject> data) {
+  if (in_debug_scope() || ignore_events()) return;
+
+  HandleScope scope(isolate_);
+  DebugScope debug_scope(this);
+  if (debug_scope.failed()) return;
+
+  // Create the script collected state object.
+  Handle<Object> event_data;
+  // Bail out and don't call debugger if exception.
+  if (!MakeAsyncTaskEvent(data).ToHandle(&event_data)) return;
+
+  // Process debug event.
+  ProcessDebugEvent(v8::AsyncTaskEvent,
+                    Handle<JSObject>::cast(event_data),
+                    true);
+}
+
+
 void Debug::ProcessDebugEvent(v8::DebugEvent event,
                               Handle<JSObject> event_data,
                               bool auto_continue) {