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

test/cctest/test-strings.cc

 // Copyright 2012 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 1490 matching lines @@
   Handle<String> arg0 = isolate->factory()->NewStringFromAsciiChecked("arg0");
   Handle<String> arg1 = isolate->factory()->NewStringFromAsciiChecked("arg1");
   Handle<String> arg2 = isolate->factory()->NewStringFromAsciiChecked("arg2");
   Handle<String> result =
       MessageTemplate::FormatMessage(MessageTemplate::kPropertyNotFunction,
                                      arg0, arg1, arg2).ToHandleChecked();
   Handle<String> expected = isolate->factory()->NewStringFromAsciiChecked(
       "'arg0' returned for property 'arg1' of object 'arg2' is not a function");
   CHECK(String::Equals(result, expected));
 }
+
+TEST(Regress609831) {
+  CcTest::InitializeVM();
+  LocalContext context;
+  Isolate* isolate = CcTest::i_isolate();
+  {
+    HandleScope scope(isolate);
+    v8::Local<v8::Value> result = CompileRun(
+        "String.fromCharCode(32, 32, 32, 32, 32, "
+        "32, 32, 32, 32, 32, 32, 32, 32, 32, 32, "
+        "32, 32, 32, 32, 32, 32, 32, 32, 32, 32)");
+    CHECK(v8::Utils::OpenHandle(*result)->IsSeqOneByteString());
+  }
+  {
+    HandleScope scope(isolate);
+    v8::Local<v8::Value> result = CompileRun(
+        "String.fromCharCode(432, 432, 432, 432, 432, "
+        "432, 432, 432, 432, 432, 432, 432, 432, 432, "
+        "432, 432, 432, 432, 432, 432, 432, 432, 432)");
+    CHECK(v8::Utils::OpenHandle(*result)->IsSeqTwoByteString());
+  }
+}