[proxies] Make Object.{freeze,seal} behave correctly for proxies.

test/mjsunit/es7/object-observe.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 332 matching lines @@
 Object.defineProperty(obj, 'd', {
   writable: false,
   configurable: false,
   value: 'd'
 });
 Object.observe(obj, observer.callback);
 Object.freeze(obj);
 
 Object.deliverChangeRecords(observer.callback);
 observer.assertCallbackRecords([
+  { object: obj, type: 'preventExtensions' },
   { object: obj, type: 'reconfigure', name: 'a' },
   { object: obj, type: 'reconfigure', name: 'b' },
   { object: obj, type: 'reconfigure', name: 'c' },
-  { object: obj, type: 'preventExtensions' },
 ]);
 
 reset();
 var obj = { foo: 'bar'};
 Object.freeze(obj);
 Object.observe(obj, observer.callback);
 Object.freeze(obj);
 Object.deliverChangeRecords(observer.callback);
 observer.assertNotCalled();
 
@@ skipping 13 matching lines @@
 Object.defineProperty(obj, 'd', {
   writable: false,
   configurable: false,
   value: 'd'
 });
 Object.observe(obj, observer.callback);
 Object.seal(obj);
 
 Object.deliverChangeRecords(observer.callback);
 observer.assertCallbackRecords([
+  { object: obj, type: 'preventExtensions' },
   { object: obj, type: 'reconfigure', name: 'a' },
   { object: obj, type: 'reconfigure', name: 'b' },
-  { object: obj, type: 'preventExtensions' },
 ]);
 
 reset();
 var obj = { foo: 'bar'};
 Object.seal(obj);
 Object.observe(obj, observer.callback);
 Object.seal(obj);
 Object.deliverChangeRecords(observer.callback);
 observer.assertNotCalled();
 
@@ skipping 1453 matching lines @@
   var ex;
   try {
     Object.observe({}, function(){}, "not an object");
   } catch (e) {
     ex = e;
   }
   assertInstanceof(ex, TypeError);
   assertEquals("Third argument to Object.observe must be an array of strings.",
                ex.message);
 })()