[esnext] prototype runtime implementation for async functions

src/code-stubs.h

Index: src/code-stubs.h
diff --git a/src/code-stubs.h b/src/code-stubs.h
index 6ed5760b6243c6896f29a2ea3d4232aaad26d5dc..bd7ff7ad5cde1f32e9891ef5b39c8b2f2ed3bf8a 100644
--- a/src/code-stubs.h
+++ b/src/code-stubs.h
@@ -1024,7 +1024,7 @@ class FastNewClosureStub : public HydrogenCodeStub {
  private:
   STATIC_ASSERT(LANGUAGE_END == 3);
   class LanguageModeBits : public BitField<LanguageMode, 0, 2> {};
-  class FunctionKindBits : public BitField<FunctionKind, 2, 8> {};
+  class FunctionKindBits : public BitField<FunctionKind, 2, 9> {};
 
   DEFINE_CALL_INTERFACE_DESCRIPTOR(FastNewClosure);
   DEFINE_HYDROGEN_CODE_STUB(FastNewClosure, HydrogenCodeStub);