[snapshot] Move builtins generation into mksnapshot

src/builtins/setup-builtins.h

+// Copyright 2017 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.
+
+namespace v8 {
+namespace internal {
+
+class Builtins;
+class Code;
+class Isolate;
+
+// This class is an abstraction layer around generation of compiled builtins.
+// There are three implementations to choose from (at link time):
+// - setup-builtins-deserialize.cc: always loads builtins from snapshot.
+// - setup-builtins-full.cc: always generates builtins.
+// - setup-builtins-for-tests.cc: does the one or the other, controlled by
+//                                the |create_heap_objects| flag.
+// The actual implementation of builtins generation is in
+// setup-builtins-internal.cc, and is linked in by the latter two.
+class SetupBuiltinsDelegate {
+ public:
+  SetupBuiltinsDelegate() {}
+  virtual ~SetupBuiltinsDelegate() {}
+
+  virtual void SetupBuiltins(Isolate* isolate, bool create_heap_objects);
+
+ protected:
+  static void SetupBuiltinsInternal(Isolate* isolate);
+  static void AddBuiltin(Builtins* builtins, int index, Code* code);
+};
+
+}  // namespace internal
+}  // namespace v8