Clear invalid field maps in PropertyAccessInfo.

test/mjsunit/regress/regress-363956.js

Index: test/mjsunit/regress/regress-363956.js
diff --git a/test/mjsunit/regress/regress-355486.js b/test/mjsunit/regress/regress-363956.js
similarity index 60%
copy from test/mjsunit/regress/regress-355486.js
copy to test/mjsunit/regress/regress-363956.js
index 55362a13416335b72bfa1ff92bc29f7a04edbd65..76d6728c02eb1cf1549af7b463c254dbb4602a7b 100644
--- a/test/mjsunit/regress/regress-355486.js
+++ b/test/mjsunit/regress/regress-363956.js
@@ -4,10 +4,9 @@
 
 // Flags: --allow-natives-syntax
 
-function f() { var v = arguments[0]; }
-function g() { f(); }
-
-g();
-g();
-%OptimizeFunctionOnNextCall(g);
-g();
+function Fuu() { this.x = this.x.x; }
+Fuu.prototype.x = {x: 1}
+new Fuu();
+new Fuu();
+%OptimizeFunctionOnNextCall(Fuu);
+new Fuu();