[builtins] Add ReturnReceiver builtin

src/builtins/builtins-promise.cc

 // Copyright 2016 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.
 
 #include "src/builtins/builtins-promise.h"
 #include "src/builtins/builtins-utils.h"
 #include "src/builtins/builtins.h"
 #include "src/code-factory.h"
 #include "src/code-stub-assembler.h"
 #include "src/promise-utils.h"
@@ skipping 973 matching lines @@
 
     GotoUnless(is_debug_active, &out);
     CallRuntime(Runtime::kDebugPopPromise, context);
     Goto(&out);
 
     Bind(&out);
     Return(UndefinedConstant());
   }
 }
 
+TF_BUILTIN(PromiseSpeciesGetter, PromiseBuiltinsAssembler) {

[adamk, 2016/12/20 23:03:12]

Seems like we should only need one of these builtins (not one for Promise, one
for RegExp, etc). Maybe put it in builtins-internal.cc?

[caitp, 2016/12/20 23:58:05]

%IteratorPrototype%[@@iterator] can reuse this code, too. 

+  // 1. Return the this value
+  Node* const receiver = Parameter(0);
+  Return(receiver);
+}
+
 }  // namespace internal
 }  // namespace v8