[async-iteration] implement Async-from-Sync Iterator

src/objects-debug.cc

Index: src/objects-debug.cc
diff --git a/src/objects-debug.cc b/src/objects-debug.cc
index 5d032d152e7fa6b0b06c4831e56cb984cd3230ef..f26c27ad1b921b01ebce8dfe2c450465d313fc3a 100644
--- a/src/objects-debug.cc
+++ b/src/objects-debug.cc
@@ -194,6 +194,9 @@ void HeapObject::HeapObjectVerify() {
     case JS_STRING_ITERATOR_TYPE:
       JSStringIterator::cast(this)->JSStringIteratorVerify();
       break;
+    case JS_ASYNC_FROM_SYNC_ITERATOR_TYPE:
+      JSAsyncFromSyncIterator::cast(this)->JSAsyncFromSyncIteratorVerify();
+      break;
     case JS_WEAK_MAP_TYPE:
       JSWeakMap::cast(this)->JSWeakMapVerify();
       break;
@@ -884,6 +887,12 @@ void JSStringIterator::JSStringIteratorVerify() {
   CHECK_LE(index(), String::kMaxLength);
 }
 
+void JSAsyncFromSyncIterator::JSAsyncFromSyncIteratorVerify() {
+  CHECK(IsJSAsyncFromSyncIterator());
+  JSObjectVerify();
+  VerifyHeapPointer(sync_iterator());
+}
+
 void JSWeakSet::JSWeakSetVerify() {
   CHECK(IsJSWeakSet());
   JSObjectVerify();