Add File.copy(Sync) to dart:io.

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 36 matching lines @@
   V(File_LengthFromPath, 1)                                                    \
   V(File_Stat, 1)                                                              \
   V(File_LastModified, 1)                                                      \
   V(File_Flush, 1)                                                             \
   V(File_Create, 1)                                                            \
   V(File_CreateLink, 2)                                                        \
   V(File_LinkTarget, 1)                                                        \
   V(File_Delete, 1)                                                            \
   V(File_DeleteLink, 1)                                                        \
   V(File_Rename, 2)                                                            \
+  V(File_Copy, 2)                                                              \
   V(File_RenameLink, 2)                                                        \
   V(File_ResolveSymbolicLinks, 1)                                              \
   V(File_OpenStdio, 1)                                                         \
   V(File_GetStdioHandleType, 1)                                                \
   V(File_GetType, 2)                                                           \
   V(File_AreIdentical, 2)                                                      \
   V(FileSystemWatcher_CloseWatcher, 1)                                         \
   V(FileSystemWatcher_GetSocketId, 2)                                          \
   V(FileSystemWatcher_InitWatcher, 0)                                          \
   V(FileSystemWatcher_IsSupported, 0)                                          \
@@ skipping 47 matching lines @@
     // 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", static_cast<int>(length), chars);
   }
 }
 
 }  // namespace bin
 }  // namespace dart