[builtins] FastNewClosureStub becomes a builtin.

src/builtins/builtins-constructor.h

+// 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/code-stub-assembler.h"
+
+namespace v8 {
+namespace internal {
+
+typedef compiler::Node Node;
+typedef compiler::CodeAssemblerState CodeAssemblerState;
+
+class ConstructorBuiltinsAssembler : public CodeStubAssembler {
+ public:
+  explicit ConstructorBuiltinsAssembler(CodeAssemblerState* state)
+      : CodeStubAssembler(state) {}
+
+  Node* EmitFastNewClosure(Node* shared_info, Node* context);
+};
+
+}  // namespace internal
+}  // namespace v8