Do not export natives to runtime via js builtins object.

src/bootstrapper.h

 // Copyright 2014 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_BOOTSTRAPPER_H_
 #define V8_BOOTSTRAPPER_H_
 
 #include "src/factory.h"
 
 namespace v8 {
@@ skipping 100 matching lines @@
 
   static bool CompileNative(Isolate* isolate, Vector<const char> name,
                             Handle<JSObject> receiver, Handle<String> source,
                             int argc, Handle<Object> argv[]);
   static bool CompileBuiltin(Isolate* isolate, int index);
   static bool CompileExperimentalBuiltin(Isolate* isolate, int index);
   static bool CompileExtraBuiltin(Isolate* isolate, int index);
   static bool CompileCodeStubBuiltin(Isolate* isolate, int index);
   static bool InstallCodeStubNatives(Isolate* isolate);
 
+  static void ImportNatives(Isolate* isolate, Handle<JSObject> container);
+  static void ImportExperimentalNatives(Isolate* isolate,
+                                        Handle<JSObject> container);
+
  private:
   Isolate* isolate_;
   typedef int NestingCounterType;
   NestingCounterType nesting_;
   SourceCodeCache extensions_cache_;
 
   friend class BootstrapperActive;
   friend class Isolate;
   friend class NativesExternalStringResource;
 
@@ skipping 36 matching lines @@
   size_t length() const override { return length_; }
 
  private:
   const char* data_;
   size_t length_;
 };
 
 }}  // namespace v8::internal
 
 #endif  // V8_BOOTSTRAPPER_H_