Revert of [runtime] Remove useless IN builtin.

src/runtime/runtime-numbers.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/arguments.h"
 #include "src/base/bits.h"
 #include "src/bootstrapper.h"
 #include "src/codegen.h"
@@ skipping 530 matching lines @@
 
 
 RUNTIME_FUNCTION(Runtime_IsSmi) {
   SealHandleScope shs(isolate);
   DCHECK(args.length() == 1);
   CONVERT_ARG_CHECKED(Object, obj, 0);
   return isolate->heap()->ToBoolean(obj->IsSmi());
 }
 
 
+RUNTIME_FUNCTION(Runtime_IsNonNegativeSmi) {
+  SealHandleScope shs(isolate);
+  DCHECK(args.length() == 1);
+  CONVERT_ARG_CHECKED(Object, obj, 0);
+  return isolate->heap()->ToBoolean(obj->IsSmi() &&
+                                    Smi::cast(obj)->value() >= 0);
+}
+
+
 RUNTIME_FUNCTION(Runtime_GetRootNaN) {
   SealHandleScope shs(isolate);
   DCHECK(args.length() == 0);
   return isolate->heap()->nan_value();
 }
 }  // namespace internal
 }  // namespace v8