Fix: make string indexing work with Infinity.

test/mjsunit/string-charat.js

 // Copyright 2008 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 23 matching lines @@
 function basicTest() {
   assertEquals("t", s.charAt());
   assertEquals("t", s.charAt("string"));
   assertEquals("t", s.charAt(null));
   assertEquals("t", s.charAt(void 0));
   assertEquals("t", s.charAt(false));
   assertEquals("e", s.charAt(true));
   assertEquals("", s.charAt(-1));
   assertEquals("", s.charAt(4));
   assertEquals("", s.charAt(slowIndexOutOfRange));
+  assertEquals("", s.charAt(1/0));
+  assertEquals("", s.charAt(-1/0));
   assertEquals("t", s.charAt(0));
   assertEquals("t", s.charAt(-0.0));
   assertEquals("t", s.charAt(0.4));
   assertEquals("e", s.charAt(slowIndex1));
   assertEquals("s", s.charAt(slowIndex2));
   assertEquals("t", s.charAt(3));
   assertEquals("t", s.charAt(3.4));
   assertEquals("t", s.charAt(NaN));
 
   assertEquals(116, s.charCodeAt());
   assertEquals(116, s.charCodeAt("string"));
   assertEquals(116, s.charCodeAt(null));
   assertEquals(116, s.charCodeAt(void 0));
   assertEquals(116, s.charCodeAt(false));
   assertEquals(101, s.charCodeAt(true));
   assertEquals(116, s.charCodeAt(0));
   assertEquals(116, s.charCodeAt(-0.0));
   assertEquals(116, s.charCodeAt(0.4));
   assertEquals(101, s.charCodeAt(slowIndex1));
   assertEquals(115, s.charCodeAt(slowIndex2));
   assertEquals(116, s.charCodeAt(3));
   assertEquals(116, s.charCodeAt(3.4));
   assertEquals(116, s.charCodeAt(NaN));
   assertTrue(isNaN(s.charCodeAt(-1)));
   assertTrue(isNaN(s.charCodeAt(4)));
   assertTrue(isNaN(s.charCodeAt(slowIndexOutOfRange)));
+  assertTrue(isNaN(s.charCodeAt(1/0)));
+  assertTrue(isNaN(s.charCodeAt(-1/0)));
 }
 basicTest();
 
 // Make sure enough of the one-char string cache is filled.
 var alpha = ['@'];
 for (var i = 1; i < 128; i++) {
   var c = String.fromCharCode(i);
   alpha[i] = c.charAt(0);
 }
 var alphaStr = alpha.join("");
@@ skipping 155 matching lines @@
       oldResult = result;
       String.prototype.charCodeAt = function() { return 42; };
     }
     result = s.charCodeAt(1);
   }
   assertEquals(42, result);
   assertEquals(101, oldResult);
   delete String.prototype.charCodeAt;  // Restore the default.
 }
 testPrototypeChange_charCodeAt();