Fix GenerateNegativeLookup to work with non-symbols as a dictionary key.

test/mjsunit/call-stub.js

 // Copyright 2010 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 31 matching lines @@
 for (var i = 1; i < 100; i++) {
   if (i == 50) {
     h.m = function() {
       return 2;
     };
   } else if (i == 70) {
     delete h.m;
   }
   assertEquals(i < 50 || i >= 70 ? 1 : 2, h.m());
 }
+
+
+var nonsymbol = 'wwwww '.split(' ')[0];
+Hash.prototype.wwwww = Hash.prototype.m;
+
+for (var i = 1; i < 100; i++) {
+  if (i == 50) {
+    h[nonsymbol] = function() {
+      return 2;
+    };
+  } else if (i == 70) {
+    delete h[nonsymbol];
+  }
+  assertEquals(i < 50 || i >= 70 ? 1 : 2, h.wwwww());
+}