[async await] Fix debug async task event

If the catch prediction machinery in the middle of some async op, we
shouldn't send invalid events to the debugger.

Instead of sending events with an undefined id, we don't send them at
all.

Review-Url: https://codereview.chromium.org/2417093003
Cr-Commit-Position: refs/heads/master@{#40327}

src/js/async-await.js

@@ -158,11 +158,16 @@ function AsyncFunctionPromiseRelease(promise) {
   if (DEBUG_IS_ACTIVE) {
     // Cancel
     var id = GET_PRIVATE(promise, promiseAsyncStackIDSymbol);
-    %DebugAsyncTaskEvent({
-      type: "cancel",
-      id: id,
-      name: "async function",
-    });
+
+    // Don't send invalid events when catch prediction is turned on in
+    // the middle of some async operation.
+    if (!IS_UNDEFINED(id)) {
+      %DebugAsyncTaskEvent({
+        type: "cancel",
+        id: id,
+        name: "async function",
+      });
+    }
     // Pop the Promise under construction in an async function on
     // from catch prediction stack.
     %DebugPopPromise();

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

@@ -43,6 +43,7 @@ function assertLog(msg) {
 function listener(event, exec_state, event_data, data) {
   if (event != Debug.DebugEvent.AsyncTaskEvent) return;
   try {
+    if ("Promise.resolve" == event_data.name()) return;
     if (base_id < 0)
       base_id = event_data.id();
     var id = event_data.id() - base_id + 1;
@@ -73,3 +74,24 @@ resolver();
 %RunMicrotasks();
 
 assertNull(exception);
+
+Debug.clearBreakOnUncaughtException();
+Debug.setListener(null);
+
+var resolve;
+var turnOnListenerPromise = new Promise(r => resolve = r);
+async function confused() {
+  await turnOnListenerPromise;
+  throw foo
+}
+
+confused();
+
+Promise.resolve().then(() => {
+  Debug.setListener(listener);
+  Debug.setBreakOnUncaughtException();
+  resolve();
+});
+
+%RunMicrotasks();
+assertNull(exception);