Fix regression in regexp-caching.html

src/regexp-delay.js

Index: src/regexp-delay.js
===================================================================
--- src/regexp-delay.js	(revision 1389)
+++ src/regexp-delay.js	(working copy)
@@ -318,7 +318,8 @@
     return IS_UNDEFINED(regExpInput) ? "" : regExpInput;
   }
   function RegExpSetInput(string) {
-    lastMatchInfo[lastMatchInfo[REGEXP_NUMBER_OF_CAPTURES] + 2] = string;
+    lastMatchInfo[lastMatchInfo[REGEXP_NUMBER_OF_CAPTURES] + 2] =
+        ToString(string);
   };
 
   %DefineAccessor($RegExp, 'input', GETTER, RegExpGetInput, DONT_DELETE);