Refactor Future constructors.

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 40 matching lines @@
         onPauseStateChange: _onPauseStateChange);
   }
 
   Future _closeFile() {
     Future closeFuture;
     if (_openedFile != null) {
       Future closeFuture = _openedFile.close();
       _openedFile = null;
       return closeFuture;
     } else {
-      return new Future.immediate(null);
+      return new Future.value();
     }
   }
 
   void _readBlock() {
     // Don't start a new read if one is already in progress.
     if (_readInProgress) return;
     _readInProgress = true;
     _openedFile.length()
       .then((length) {
         if (_position >= length) {
@@ skipping 27 matching lines @@
           _unsubscribed = true;
         }
       });
   }
 
   void _start() {
     Future<RandomAccessFile> openFuture;
     if (_path != null) {
       openFuture = new File(_path).open(mode: FileMode.READ);
     } else {
-      openFuture = new Future.immediate(_File._openStdioSync(0));
+      openFuture = new Future.value(_File._openStdioSync(0));
     }
     openFuture
       .then((RandomAccessFile opened) {
         _openedFile = opened;
         _readBlock();
       })
       .catchError((e) {
         _controller.addError(e);
         _controller.close();
       });
@@ skipping 31 matching lines @@
   File _file;
   Future<RandomAccessFile> _openFuture;
   StreamSubscription _subscription;
 
   _FileStreamConsumer(File this._file, FileMode mode) {
     _openFuture = _file.open(mode: mode);
   }
 
   _FileStreamConsumer.fromStdio(int fd) {
     assert(1 <= fd && fd <= 2);
-    _openFuture = new Future.immediate(_File._openStdioSync(fd));
+    _openFuture = new Future.value(_File._openStdioSync(fd));
   }
 
   Future<File> consume(Stream<List<int>> stream) {
     return addStream(stream).then((_) => close());
   }
 
   Future<File> addStream(Stream<List<int>> stream) {
     Completer<File> completer = new Completer<File>();
     _openFuture
       .then((openedFile) {
@@ skipping 382 matching lines @@
   }
 
   Future<File> writeAsBytes(List<int> bytes,
                             {FileMode mode: FileMode.WRITE}) {
     try {
       IOSink<File> sink = openWrite(mode: mode);
       sink.add(bytes);
       sink.close();
       return sink.done.then((_) => this);;
     } catch (e) {
-      return new Future.immediateError(e);
+      return new Future.error(e);
     }
   }
 
   void writeAsBytesSync(List<int> bytes, {FileMode mode: FileMode.WRITE}) {
     RandomAccessFile opened = openSync(mode: mode);
     opened.writeListSync(bytes, 0, bytes.length);
     opened.closeSync();
   }
 
   Future<File> writeAsString(String contents,
@@ skipping 479 matching lines @@
           new FileIOException("File closed '$_path'"));
     });
     return completer.future;
   }
 
   final String _path;
   int _id;
 
   SendPort _fileService;
 }