Native context: use import/export for Object observe related functions.

src/js/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, extrasUtils) {
 
 "use strict";
 
 %CheckIsBootstrapping();
 
@@ skipping 166 matching lines @@
     "InnerArrayReduceRight",
     "InnerArrayReverse",
     "InnerArraySome",
     "InnerArraySort",
     "InnerArrayToLocaleString",
     "IsNaN",
     "MathMax",
     "MathMin",
     "ObjectIsFrozen",
     "ObjectDefineProperty",
+    "ObserveArrayMethods",
+    "ObserveObjectMethods",
     "OwnPropertyKeys",
     "SymbolToString",
     "ToNameArray",
     // From runtime:
     "is_concat_spreadable_symbol",
     "iterator_symbol",
     "promise_status_symbol",
     "promise_value_symbol",
     "reflect_apply",
     "reflect_construct",
@@ skipping 106 matching lines @@
 
 extrasUtils.uncurryThis = function uncurryThis(func) {
   return function(thisArg) {
     return %Apply(func, thisArg, arguments, 1, arguments.length - 1);
   };
 };
 
 %ToFastProperties(extrasUtils);
 
 })