Make DescriptorArray::IsMoreGeneralThan() and DescriptorArray::Merge() compatible again.

test/mjsunit/regress/regress-365172-3.js

Index: test/mjsunit/regress/regress-365172-3.js
diff --git a/test/mjsunit/regress/regress-365172-3.js b/test/mjsunit/regress/regress-365172-3.js
new file mode 100644
index 0000000000000000000000000000000000000000..103d3d03b8ac5fa00038c62eabb9f4ad7bde30dc
--- /dev/null
+++ b/test/mjsunit/regress/regress-365172-3.js
@@ -0,0 +1,14 @@
+// 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: --expose-gc --track-field-types
+
+function f1(a) { return {x:a, v:''}; }
+function f2(a) { return {x:{v:a}, v:''}; }
+function f3(a) { return {x:[], v:{v:''}}; }
+f3([0]);
+a = f1(1);
+a.__defineGetter__('v', function() { gc(); return f2(this); });
+a.v;
+f3(1);