[proxy] Reload the initial map after prototype lookup on constructable

test/mjsunit/regress/regress-crbug-578039-Proxy_construct_prototype_change.js

Index: test/mjsunit/regress/regress-crbug-578039-Proxy_construct_prototype_change.js
diff --git a/test/mjsunit/compiler/regress-572409.js b/test/mjsunit/regress/regress-crbug-578039-Proxy_construct_prototype_change.js
similarity index 51%
copy from test/mjsunit/compiler/regress-572409.js
copy to test/mjsunit/regress/regress-crbug-578039-Proxy_construct_prototype_change.js
index 126b622625ad4455b4bd2e309ee10e32eb02989e..30b3f219e9a1a733fefdac8b92a1e01b6be58f7e 100644
--- a/test/mjsunit/compiler/regress-572409.js
+++ b/test/mjsunit/regress/regress-crbug-578039-Proxy_construct_prototype_change.js
@@ -2,9 +2,13 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-var o = function() {};
-function f() {
-  var lit = { __proto__: o  };
-  o instanceof RegExp;
-}
-f();
+
+function target() {};
+
+var proxy = new Proxy(target, {
+  get() {
+    // Reset the initial map of the target.
+    target.prototype = 123;
+  }});
+
+new proxy();