Remove 'dart:io' import in builtin.dart

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 51 matching lines @@
   V(File_ResolveSymbolicLinks, 1)                                              \
   V(File_OpenStdio, 1)                                                         \
   V(File_GetStdioHandleType, 1)                                                \
   V(File_GetType, 2)                                                           \
   V(File_AreIdentical, 2)                                                      \
   V(Logger_PrintString, 1)                                                     \
   V(Builtin_LoadScript, 4)                                                     \
   V(Builtin_AsyncLoadError, 3)                                                 \
   V(Builtin_DoneLoading, 0)                                                    \
   V(Builtin_NativeLibraryExtension, 0)                                         \
+  V(Builtin_GetCurrentDirectory, 0)                                            \
 
 
 BUILTIN_NATIVE_LIST(DECLARE_FUNCTION);
 
 static struct NativeEntries {
   const char* name_;
   Dart_NativeFunction function_;
   int argument_count_;
 } BuiltinEntries[] = {
   BUILTIN_NATIVE_LIST(REGISTER_FUNCTION)
@@ skipping 52 matching lines @@
   } else {
     // Uses fwrite to support printing NUL bytes.
     fwrite(chars, 1, length, stdout);
     fputs("\n", stdout);
   }
   fflush(stdout);
 }
 
 }  // namespace bin
 }  // namespace dart