[esnext] implement frontend changes for async/await proposal

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index dd2d2df384bd4c64ab41759832154472cf59f8ff..7a24436f0c1050bba25161128c12174e75eee4a4 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -5786,6 +5786,7 @@ BOOL_ACCESSORS(SharedFunctionInfo, compiler_hints, dont_crankshaft,
 BOOL_ACCESSORS(SharedFunctionInfo, compiler_hints, dont_flush, kDontFlush)
 BOOL_ACCESSORS(SharedFunctionInfo, compiler_hints, is_arrow, kIsArrow)
 BOOL_ACCESSORS(SharedFunctionInfo, compiler_hints, is_generator, kIsGenerator)
+BOOL_ACCESSORS(SharedFunctionInfo, compiler_hints, is_async, kIsAsyncFunction)
 BOOL_ACCESSORS(SharedFunctionInfo, compiler_hints, is_concise_method,
                kIsConciseMethod)
 BOOL_ACCESSORS(SharedFunctionInfo, compiler_hints, is_getter_function,
@@ -5795,6 +5796,10 @@ BOOL_ACCESSORS(SharedFunctionInfo, compiler_hints, is_setter_function,
 BOOL_ACCESSORS(SharedFunctionInfo, compiler_hints, is_default_constructor,
                kIsDefaultConstructor)
 
+inline bool SharedFunctionInfo::is_resumable() const {
+  return is_generator() || is_async();
+}
+
 bool Script::HasValidSource() {
   Object* src = this->source();
   if (!src->IsString()) return true;