[builtins] Migrate String.fromCharCode to C++.

test/mjsunit/string-fromcharcode.js

Index: test/mjsunit/string-fromcharcode.js
diff --git a/test/mjsunit/string-fromcharcode.js b/test/mjsunit/string-fromcharcode.js
index ad3f7a96fb140310f1fe4de1af71b1d7d473079f..ac51682b72cfc7bc9f6138db58a642c5dd52a48d 100644
--- a/test/mjsunit/string-fromcharcode.js
+++ b/test/mjsunit/string-fromcharcode.js
@@ -103,11 +103,6 @@ for (var i = 0; i < 10; i++) {
   test(i);
 }
 
-assertEquals("AAAA", String.fromCharCode(65, 65, 65, 65));
-assertEquals("AAAA", String.fromCharCode(65, 65, 65, 65));
-%OptimizeFunctionOnNextCall(String.fromCharCode);
-assertEquals("AAAA", String.fromCharCode(65, 65, 65, 65));
-
 // Test the custom IC works correctly when the map changes.
 for (var i = 0; i < 10; i++) {
   var expected = (i < 5) ? " " : 42;