Do not generalize field representations when making elements kind or observed transition.

test/mjsunit/regress/regress-448711.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.
-
+//
 // Flags: --allow-natives-syntax
 
-function g() {
-  throw 0;
+function f() {
+  this.a = { text: "Hello!" };
 }
-
-function f() {
-  g();
-  while (1) {}
-}
-
-assertThrows(function () { f(); });
+var v4 = new f();
+var v7 = new f();
+v7.b = {};
+Object.defineProperty(v4, '2', {});
+var v6 = new f();
+v6.a = {};