Improve stack traces for async functions

test/mjsunit/harmony/debug-async-function-async-task-event.js

Index: test/mjsunit/harmony/debug-async-function-async-task-event.js
diff --git a/test/mjsunit/harmony/debug-async-function-async-task-event.js b/test/mjsunit/harmony/debug-async-function-async-task-event.js
index 5e01938f361b6ef7ecf123cb2aecd5901cf71da0..90e13d8659a3f81856e1bdc3b8f972405f3cfe9c 100644
--- a/test/mjsunit/harmony/debug-async-function-async-task-event.js
+++ b/test/mjsunit/harmony/debug-async-function-async-task-event.js
@@ -5,9 +5,14 @@
 // Flags: --harmony-async-await --expose-debug-as debug --allow-natives-syntax
 
 // The test observes the callbacks that async/await makes to the inspector
-// to make accurate stack traces. The limited number of events is an
-// indirect indication that we are not doing extra Promise processing that
-// could be associated with memory leaks (v8:5380).
+// to make accurate stack traces. The pattern is based on saving a stack once
+// with enqueueRecurring and restoring it multiple times.
+
+// Additionally, the limited number of events is an indirect indication that
+// we are not doing extra Promise processing that could be associated with memory
+// leaks (v8:5380). In particular, no stacks are saved and restored for extra
+// Promise handling on throwaway Promises.
+
 // TODO(littledan): Write a test that demonstrates that the memory leak in
 // the exception case is fixed.
 
@@ -16,14 +21,14 @@ Debug = debug.Debug;
 var base_id = -1;
 var exception = null;
 var expected = [
-  'enqueue #1',
+  'enqueueRecurring #1',
   'willHandle #1',
   'then #1',
-  'enqueue #2',
   'didHandle #1',
-  'willHandle #2',
+  'willHandle #1',
   'then #2',
-  'didHandle #2',
+  'cancel #1',
+  'didHandle #1',
 ];
 
 function assertLog(msg) {
@@ -41,8 +46,7 @@ function listener(event, exec_state, event_data, data) {
     if (base_id < 0)
       base_id = event_data.id();
     var id = event_data.id() - base_id + 1;
-    assertTrue("Promise.resolve" == event_data.name() ||
-               "PromiseResolveThenableJob" == event_data.name());
+    assertTrue("async function" == event_data.name());
     assertLog(event_data.type() + " #" + id);
   } catch (e) {
     print(e + e.stack)