Make sure we always try to make prototypes fast again when transitioning accessors

test/mjsunit/regress/regress-crbug-605060.js

Index: test/mjsunit/regress/regress-crbug-605060.js
diff --git a/test/mjsunit/regress/regress-crbug-605060.js b/test/mjsunit/regress/regress-crbug-605060.js
new file mode 100644
index 0000000000000000000000000000000000000000..d2dc79a310bf52456bf12639d3c360520be36cc0
--- /dev/null
+++ b/test/mjsunit/regress/regress-crbug-605060.js
@@ -0,0 +1,10 @@
+// Copyright 2016 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
+
+Array.prototype.__defineGetter__('map', function(){});
+Array.prototype.__defineGetter__('map', function(){});
+Array.prototype.__defineGetter__('map', function(){});
+assertTrue(%HasFastProperties(Array.prototype));