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

runtime/bin/file_macos.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 "platform/globals.h"
 #if defined(TARGET_OS_MACOS)
 
 #include "bin/file.h"
 
 #include <errno.h>  // NOLINT
 #include <fcntl.h>  // NOLINT
+#include <copyfile.h>  // NOLINT
 #include <sys/stat.h>  // NOLINT
 #include <unistd.h>  // NOLINT
 #include <libgen.h>  // NOLINT
 #include <limits.h>  // NOLINT
 
 #include "bin/builtin.h"
 #include "bin/fdutils.h"
 #include "bin/log.h"
 
 
@@ skipping 192 matching lines @@
     return TEMP_FAILURE_RETRY(rename(old_path, new_path)) == 0;
   } else if (type == kIsDirectory) {
     errno = EISDIR;
   } else {
     errno = EINVAL;
   }
   return false;
 }
 
 
+bool File::Copy(const char* old_path, const char* new_path) {
+  File::Type type = File::GetType(old_path, true);
+  if (type == kIsFile) {
+    return copyfile(old_path, new_path, NULL, COPYFILE_ALL) == 0;
+  } else if (type == kIsDirectory) {
+    errno = EISDIR;
+  } else {
+    errno = ENOENT;
+  }
+  return false;
+}
+
+
 off64_t File::LengthFromPath(const char* name) {
   struct stat st;
   if (TEMP_FAILURE_RETRY(stat(name, &st)) == 0) {
     return st.st_size;
   }
   return -1;
 }
 
 
 void File::Stat(const char* name, int64_t* data) {
@@ skipping 124 matching lines @@
   return (file_1_info.st_ino == file_2_info.st_ino &&
           file_1_info.st_dev == file_2_info.st_dev) ?
       File::kIdentical :
       File::kDifferent;
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_MACOS)