[promises] Move PromiseResolveThenableJob to c++

src/js/promise.js

Index: src/js/promise.js
diff --git a/src/js/promise.js b/src/js/promise.js
index e020028c244f8f0d45bf429316ae916757012de5..2daaf16975d8cd9363c8d47f49f22fd7933b8966 100644
--- a/src/js/promise.js
+++ b/src/js/promise.js
@@ -283,30 +283,29 @@ function ResolvePromise(promise, resolution) {
     }
 
     if (IS_CALLABLE(then)) {
-      // PromiseResolveThenableJob
-      var id;
-      var name = "PromiseResolveThenableJob";
-      var instrumenting = DEBUG_IS_ACTIVE;
-      %EnqueueMicrotask(function() {
-        if (instrumenting) {
-          %DebugAsyncTaskEvent({ type: "willHandle", id: id, name: name });
-        }
-        // These resolving functions simply forward the exception, so
-        // don't create a new debugEvent.
-        var callbacks = CreateResolvingFunctions(promise, false);
-        try {
-          %_Call(then, resolution, callbacks.resolve, callbacks.reject);
-        } catch (e) {
-          %_Call(callbacks.reject, UNDEFINED, e);
-        }
-        if (instrumenting) {
-          %DebugAsyncTaskEvent({ type: "didHandle", id: id, name: name });
-        }
-      });
-      if (instrumenting) {
+      var callbacks = CreateResolvingFunctions(promise, false);
+      var id, before_debug_event, after_debug_event;
+      if (DEBUG_IS_ACTIVE) {
         id = ++lastMicrotaskId;
-        %DebugAsyncTaskEvent({ type: "enqueue", id: id, name: name });
+        before_debug_event = {
+          type: "willHandle",
+          id: id,
+          name: "PromiseResolveThenableJob"
+        };
+        after_debug_event = {
+          type: "didHandle",
+          id: id,
+          name: "PromiseResolveThenableJob"
+        };
+        %DebugAsyncTaskEvent({
+          type: "enqueue",
+          id: id,
+          name: "PromiseResolveThenableJob"
+        });
       }
+      %EnqueuePromiseResolveThenableJob(
+          resolution, then, callbacks.resolve, callbacks.reject,
+          before_debug_event, after_debug_event);
       return;
     }
   }
@@ -613,7 +612,7 @@ utils.InstallFunctions(GlobalPromise.prototype, DONT_ENUM, [
   "promise_has_user_defined_reject_handler", PromiseHasUserDefinedRejectHandler,
   "promise_reject", DoRejectPromise,
   "promise_resolve", ResolvePromise,
-  "promise_then", PromiseThen,
+  "promise_then", PromiseThen
 ]);
 
 // This allows extras to create promises quickly without building extra