Make the strict-mode calling convention for contextual calls the default one.

test/mjsunit/harmony/proxies-function.js

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 745 matching lines @@
 Realm.eval(realms[1], "Realm.shared.gg = this;");
 
 var fp = Proxy.createFunction({}, Realm.shared.f);
 var gp = Proxy.createFunction({}, Realm.shared.g);
 
 for (var i = 0; i < 10; i++) {
   assertEquals(Realm.shared.fg, fp());
   assertEquals(Realm.shared.gg, gp());
 
   with (this) {
-    assertEquals(Realm.shared.fg, fp());
-    assertEquals(Realm.shared.gg, gp());
+    assertEquals(this, fp());
+    assertEquals(this, gp());
   }
 
   with ({}) {
     assertEquals(Realm.shared.fg, fp());
     assertEquals(Realm.shared.gg, gp());
   }
 }