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

sdk/lib/io/file_impl.dart

 // Copyright (c) 2013, 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.
 
 part of dart.io;
 
 // Read the file in blocks of size 64k.
 const int _BLOCK_SIZE = 64 * 1024;
 
 
@@ skipping 309 matching lines @@
   external static _rename(String oldPath, String newPath);
 
   external static _renameLink(String oldPath, String newPath);
 
   File renameSync(String newPath) {
     var result = _rename(path, newPath);
     throwIfError(result, "Cannot rename file to '$newPath'", path);
     return new File(newPath);
   }
 
+  Future<File> copy(String newPath) {
+    return _IOService.dispatch(_FILE_COPY, [path, newPath]).then((response) {
+      if (_isErrorResponse(response)) {
+        throw _exceptionFromResponse(
+            response, "Cannot copy file to '$newPath'", path);
+      }
+      return new File(newPath);
+    });
+  }
+
+  external static _copy(String oldPath, String newPath);
+
+  File copySync(String newPath) {
+    var result = _copy(path, newPath);
+    throwIfError(result, "Cannot copy file to '$newPath'", path);
+    return new File(newPath);
+  }
+
   Future<RandomAccessFile> open({FileMode mode: FileMode.READ}) {
     if (mode != FileMode.READ &&
         mode != FileMode.WRITE &&
         mode != FileMode.APPEND) {
       return new Future.error(new ArgumentError());
     }
     return _IOService.dispatch(_FILE_OPEN, [path, mode._mode]).then((response) {
       if (_isErrorResponse(response)) {
         throw _exceptionFromResponse(response, "Cannot open file", path);
       }
@@ skipping 550 matching lines @@
 
   void _checkAvailable() {
     if (_asyncDispatched) {
       throw new FileSystemException("An async operation is currently pending", path);
     }
     if (closed) {
       throw new FileSystemException("File closed", path);
     }
   }
 }