Do not export natives to runtime via js builtins object.

src/prologue.js

 // 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.
 
 (function(global, utils) {
 
 "use strict";
 
 %CheckIsBootstrapping();
 
 // -----------------------------------------------------------------------
 // Utils
 
 var imports = UNDEFINED;
 var exports = UNDEFINED;
 var imports_from_experimental = UNDEFINED;
-
+var exports_to_runtime = UNDEFINED;
 
 // Export to other scripts.
 // In normal natives, this exports functions to other normal natives.
 // In experimental natives, this exports to other experimental natives and
 // to normal natives that import using utils.ImportFromExperimental.
 function Export(f) {
   f.next = exports;
   exports = f;
 };
 
 
+// Export to the native context for calls from the runtime.
+function ExportToRuntime(f) {
+  f.next = exports_to_runtime;
+  exports_to_runtime = f;
+}
+
 // Import from other scripts.
 // In normal natives, this imports from other normal natives.
 // In experimental natives, this imports from other experimental natives and
 // whitelisted exports from normal natives.
 function Import(f) {
   f.next = imports;
   imports = f;
 };
 
 
@@ skipping 106 matching lines @@
 
 var experimental_exports = UNDEFINED;
 
 function PostNatives(utils) {
   %CheckIsBootstrapping();
 
   var container = {};
   for ( ; !IS_UNDEFINED(exports); exports = exports.next) exports(container);
   for ( ; !IS_UNDEFINED(imports); imports = imports.next) imports(container);
 
+  var runtime_container = {};
+  for ( ; !IS_UNDEFINED(exports_to_runtime);
+          exports_to_runtime = exports_to_runtime.next) {
+    exports_to_runtime(runtime_container);
+  }
+  %ImportToRuntime(runtime_container);
+
   // Whitelist of exports from normal natives to experimental natives.
   var expose_to_experimental = [
     "ArrayToString",
     "GetIterator",
     "GetMethod",
     "InnerArrayEvery",
     "InnerArrayFilter",
     "InnerArrayForEach",
     "InnerArrayIndexOf",
     "InnerArrayJoin",
@@ skipping 33 matching lines @@
   for ( ; !IS_UNDEFINED(exports); exports = exports.next) {
     exports(experimental_exports);
   }
   for ( ; !IS_UNDEFINED(imports); imports = imports.next) {
     imports(experimental_exports);
   }
   for ( ; !IS_UNDEFINED(imports_from_experimental);
           imports_from_experimental = imports_from_experimental.next) {
     imports_from_experimental(experimental_exports);
   }
+  var runtime_container = {};
+  for ( ; !IS_UNDEFINED(exports_to_runtime);
+          exports_to_runtime = exports_to_runtime.next) {
+    exports_to_runtime(runtime_container);
+  }
+  %ImportExperimentalToRuntime(runtime_container);
 
   experimental_exports = UNDEFINED;
 
   utils.PostExperimentals = UNDEFINED;
   utils.PostDebug = UNDEFINED;
   utils.Import = UNDEFINED;
   utils.Export = UNDEFINED;
 };
 
 
 function PostDebug(utils) {
   for ( ; !IS_UNDEFINED(exports); exports = exports.next) {
     exports(experimental_exports);
   }
   for ( ; !IS_UNDEFINED(imports); imports = imports.next) {
     imports(experimental_exports);
   }
 
   utils.PostDebug = UNDEFINED;
   utils.PostExperimentals = UNDEFINED;
   utils.Import = UNDEFINED;
   utils.Export = UNDEFINED;
 };
 
 // -----------------------------------------------------------------------
 
 InstallFunctions(utils, NONE, [
   "Import", Import,
   "Export", Export,
+  "ExportToRuntime", ExportToRuntime,
   "ImportFromExperimental", ImportFromExperimental,
   "SetFunctionName", SetFunctionName,
   "InstallConstants", InstallConstants,
   "InstallFunctions", InstallFunctions,
   "InstallGetter", InstallGetter,
   "InstallGetterSetter", InstallGetterSetter,
   "SetUpLockedPrototype", SetUpLockedPrototype,
   "PostNatives", PostNatives,
   "PostExperimentals", PostExperimentals,
   "PostDebug", PostDebug,
 ]);
 
+// TODO(yangguo): run prologue.js before runtime.js
+ExportToRuntime(function(to) {
+  to.ToNumber = $toNumber;
+  to.ToString = $toString;
+  to.ToDetailString = $toDetailString;
+  to.ToInteger = $toInteger;
+  to.ToLength = $toLength;
+});
+
 })