[runtime] support new Proxy() instead of Proxy.create and install getPrototypeOf trap

test/mjsunit/harmony/regress/regress-405844.js

 // 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.
 //
 // Flags: --harmony-proxies --harmony-object-observe
 
-// TODO(neis): These tests are temporarily commented out because of ongoing
-// changes to the implementation of proxies.
+var proxy = new Proxy({}, { fix: function() { return {}; } });
+Object.preventExtensions(proxy);
+Object.observe(proxy, function(){});
 
-//var proxy = Proxy.create({ fix: function() { return {}; } });
-//Object.preventExtensions(proxy);
-//Object.observe(proxy, function(){});
-//
-//var functionProxy = Proxy.createFunction({ fix: function() { return {}; } }, function(){});
-//Object.preventExtensions(functionProxy);
-//Object.observe(functionProxy, function(){});
+var functionProxy = Proxy.createFunction({ fix: function() { return {}; } }, function(){});
+Object.preventExtensions(functionProxy);
+Object.observe(functionProxy, function(){});