[wasm] instantiate expressed in terms of compile

test/mjsunit/wasm/instantiate-run-basic.js

 // 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.
 
-// Flags: --expose-wasm
+// Flags: --allow-natives-syntax
 
 load("test/mjsunit/wasm/wasm-constants.js");
 load("test/mjsunit/wasm/wasm-module-builder.js");
 
-(function BasicTest() {
-  var kReturnValue = 15;
+const kReturnValue = 15;
+
+function getBuilder() {
   var builder = new WasmModuleBuilder();
 
   builder.addFunction("main", kSig_i_i)
     .addBody([kExprI32Const, kReturnValue])
     .exportFunc();
+  return builder;
+}
 
+(function BasicTest() {
+  var builder = getBuilder();
   var main = builder.instantiate().exports.main;
   assertEquals(kReturnValue, main());
 })();
+
+(function AsyncTest() {
+  var builder = getBuilder();
+  var buffer = builder.toBuffer();
+  assertPromiseResult(WebAssembly.instantiate(buffer)
+                     .then(pair => pair.instance.exports.main(), assertUnreachable)
+                     .then(result => assertEquals(kReturnValue, result), assertUnreachable));
+})();