Use int for size when printing to stdout.

runtime/bin/builtin_natives.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
 
 #include "include/dart_api.h"
 
@@ skipping 93 matching lines @@
   uint8_t* chars = NULL;
   Dart_Handle str = Dart_GetNativeArgument(args, 0);
   Dart_Handle result = Dart_StringToUTF8(str, &chars, &length);
   if (Dart_IsError(result)) {
     // TODO(turnidge): Consider propagating some errors here.  What if
     // an isolate gets interrupted by the embedder in the middle of
     // Dart_StringToUTF8?  We need to make sure not to swallow the
     // interrupt.
     Platform::PrintBlocking(stdout, "%s\n", Dart_GetError(result));
   } else {
-    Platform::PrintBlocking(stdout, "%.*s\n", length, chars);
+    Platform::PrintBlocking(stdout, "%.*s\n", static_cast<int>(length), chars);
   }
 }
 
 }  // namespace bin
 }  // namespace dart