[esnext] prototype runtime implementation for async functions

src/objects.h

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_OBJECTS_H_
 #define V8_OBJECTS_H_
 
 #include <iosfwd>
 
 #include "src/assert-scope.h"
@@ skipping 6898 matching lines @@
 
   // Indicates that code for this function cannot be compiled with Crankshaft.
   DECL_BOOLEAN_ACCESSORS(dont_crankshaft)
 
   // Indicates that code for this function cannot be flushed.
   DECL_BOOLEAN_ACCESSORS(dont_flush)
 
   // Indicates that this function is a generator.
   DECL_BOOLEAN_ACCESSORS(is_generator)
 
+  // Indicates that this function is an async function.
+  DECL_BOOLEAN_ACCESSORS(is_async)
+
   // Indicates that this function is an arrow function.
   DECL_BOOLEAN_ACCESSORS(is_arrow)
 
   // Indicates that this function is a concise method.
   DECL_BOOLEAN_ACCESSORS(is_concise_method)
 
   // Indicates that this function is a getter.
   DECL_BOOLEAN_ACCESSORS(is_getter_function)
 
   // Indicates that this function is a setter.
@@ skipping 3852 matching lines @@
     }
     return value;
   }
 };
 
 
 }  // NOLINT, false-positive due to second-order macros.
 }  // NOLINT, false-positive due to second-order macros.
 
 #endif  // V8_OBJECTS_H_