Re-land FastAccessorBuilder.

src/api-experimental.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_API_EXPERIMENTAL_H_
+#define V8_API_EXPERIMENTAL_H_
+
+#include "src/handles.h"
+
+namespace v8 {
+namespace internal {
+class Code;
+}  // internal;
+namespace experimental {
+class FastAccessorBuilder;
+}  // experimental
+
+namespace internal {
+namespace experimental {
+
+v8::internal::MaybeHandle<v8::internal::Code> BuildCodeFromFastAccessorBuilder(
+    v8::experimental::FastAccessorBuilder* fast_handler);
+
+}  // namespace experimental
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_API_EXPERIMENTAL_H_