Fix keyed stores to strings convertible to indices

test/mjsunit/harmony/proxies.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 364 matching lines @@
   assertEquals(44, p[77] = 44)
   assertEquals("77", key)
   assertEquals(44, val)
 
   assertEquals(45, (function(n) { return p[n] = 45 })("c"))
   assertEquals("c", key)
   assertEquals(45, val)
   assertEquals(46, (function(n) { return p[n] = 46 })(99))
   assertEquals("99", key)
   assertEquals(46, val)
+
+  assertEquals(47, p["0"] = 47)
+  assertEquals("0", key)
+  assertEquals(47, val)
 }
 
 TestSet({
   set: function(r, k, v) { key = k; val = v; return true }
 })
 
 TestSet({
   set: function(r, k, v) { return this.set2(r, k, v) },
   set2: function(r, k, v) { key = k; val = v; return true }
 })
@@ skipping 1922 matching lines @@
   function f() {
     return o.x;
   }
   assertEquals(10, f());
   assertEquals(10, f());
   %OptimizeFunctionOnNextCall(f);
   assertEquals(10, f());
 }
 
 TestOptWithProxyPrototype();