Fix: make string indexing work with Infinity.

test/mjsunit/string-charat.js

Index: test/mjsunit/string-charat.js
diff --git a/test/mjsunit/string-charat.js b/test/mjsunit/string-charat.js
index a14d51aa528d5101d2a8744592add488ddae04f7..f0b0566812c7be907d6f8e8ab455d6b152ac9b7d 100644
--- a/test/mjsunit/string-charat.js
+++ b/test/mjsunit/string-charat.js
@@ -41,6 +41,8 @@ function basicTest() {
   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));
@@ -67,6 +69,8 @@ function basicTest() {
   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();