Introduce debug events for Microtask queue.

test/mjsunit/es6/debug-promises-caught-all.js

 // Copyright 2014 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.
 
 // Flags: --expose-debug-as debug
 
 // Test debug events when we listen to all exceptions and
 // there is a catch handler for the exception thrown in a Promise.
 // We expect a normal Exception debug event to be triggered.
 
@@ skipping 12 matching lines @@
     log.push("throw");
     throw new Error("caught");
   });
 
 q.catch(
   function(e) {
     assertEquals("caught", e.message);
   });
 
 function listener(event, exec_state, event_data, data) {
+  if (event == Debug.DebugEvent.AsyncTaskEvent) return;
   try {
     // Ignore exceptions during startup in stress runs.
     if (step >= 1) return;
     assertEquals(["resolve", "end main", "throw"], log);
     if (event == Debug.DebugEvent.Exception) {
       assertEquals("caught", event_data.exception().message);
       assertEquals(undefined, event_data.promise());
       assertFalse(event_data.uncaught());
       step++;
     }
   } catch (e) {
     // Signal a failure with exit code 1.  This is necessary since the
     // debugger swallows exceptions and we expect the chained function
     // and this listener to be executed after the main script is finished.
     print("Unexpected exception: " + e + "\n" + e.stack);
     quit(1);
   }
 }
 
 Debug.setBreakOnException();
 Debug.setListener(listener);
 
 log.push("end main");