[string] Move String.p.toLowerCase to CSA

test/mjsunit/string-case.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 41 matching lines @@
 function test(length) {
   var str = "";
   var strLower = "";
   var strUpper = "";
   for (var i = 0; i < length; i++) {
     var c = Math.round(0x7f * Math.random());
     str += String.fromCharCode(c);
     strLower += String.fromCharCode(charCodeToLower(c));
     strUpper += String.fromCharCode(charCodeToUpper(c));
   }
-  %FlattenString(strLower);
-  %FlattenString(strUpper);
+  str = %FlattenString(str);
+  strLower = %FlattenString(strLower);
+  strUpper = %FlattenString(strUpper);
   // Sequential string.
   assertEquals(strLower, str.toLowerCase());
   assertEquals(strUpper, str.toUpperCase());
   // Cons string.
   assertEquals(strLower + strLower, (str + str).toLowerCase());
   assertEquals(strUpper + strUpper, (str + str).toUpperCase());
   // Sliced string.
   assertEquals(strLower.substring(1), str.substring(1).toLowerCase());
   assertEquals(strUpper.substring(1), str.substring(1).toUpperCase());
   // External string.
   externalizeString(str, false);
   assertEquals(strLower, str.toLowerCase());
   assertEquals(strUpper, str.toUpperCase());
 }
 
 for (var i = 1; i <= 128; i <<= 1); {
   for (var j = 0; j < 8; j++) {
     for (var k = 0; k < 3; k++) {
       test(i + j);
     }
   }
 }