Mark proxy map as unstable during fixing freezing, sealing or preventing extensions).

test/mjsunit/regress/regress-crbug-493568.js

Index: test/mjsunit/regress/regress-crbug-493568.js
diff --git a/test/mjsunit/harmony/regress/regress-crbug-448730.js b/test/mjsunit/regress/regress-crbug-493568.js
similarity index 57%
copy from test/mjsunit/harmony/regress/regress-crbug-448730.js
copy to test/mjsunit/regress/regress-crbug-493568.js
index 31d276aa839cdf649b2da1ad54138cc4f9418b81..081f4937fee396568c179cf63ccc69e63a90a382 100644
--- a/test/mjsunit/harmony/regress/regress-crbug-448730.js
+++ b/test/mjsunit/regress/regress-crbug-493568.js
@@ -4,11 +4,9 @@
 
 // Flags: --allow-natives-syntax --harmony-proxies
 
-function bar() {}
-bar({ a: Proxy.create({}) });
-function foo(x) { x.a.b == ""; }
-var x = {a: {b: "" }};
-foo(x);
-foo(x);
-%OptimizeFunctionOnNextCall(foo);
-foo(x);
+var p = Proxy.create({ fix: function() { return {}; } });
+
+var obj = {};
+obj.x = p;
+
+Object.preventExtensions(p);