Remove Encoding-enum from dart:io and add interface in dart:convert.

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 448 matching lines @@
     var result = _fullPath(path);
     throwIfError(result, "Cannot retrieve full path", path);
     return result;
   }
 
   Stream<List<int>> openRead([int start, int end]) {
     return new _FileStream(path, start, end);
   }
 
   IOSink openWrite({FileMode mode: FileMode.WRITE,
-                    Encoding encoding: Encoding.UTF_8}) {
+                    Encoding encoding: UTF8}) {
     if (mode != FileMode.WRITE &&
         mode != FileMode.APPEND) {
       throw new ArgumentError(
           "Wrong FileMode. Use FileMode.WRITE or FileMode.APPEND");
     }
     var consumer = new _FileStreamConsumer(this, mode);
     return new IOSink(consumer, encoding: encoding);
   }
 
   Future<List<int>> readAsBytes() {
@@ skipping 16 matching lines @@
     var opened = openSync();
     var builder = new BytesBuilder();
     var data;
     while ((data = opened.readSync(_BLOCK_SIZE)).length > 0) {
       builder.add(data);
     }
     opened.closeSync();
     return builder.takeBytes();
   }
 
-  Future<String> readAsString({Encoding encoding: Encoding.UTF_8}) {
+  Future<String> readAsString({Encoding encoding: UTF8}) {
     _ensureFileService();
     return readAsBytes().then((bytes) {
-      return _decodeString(bytes, encoding);
+      return encoding.decode(bytes);
     });
   }
 
-  String readAsStringSync({Encoding encoding: Encoding.UTF_8}) {
+  String readAsStringSync({Encoding encoding: UTF8}) {
     List<int> bytes = readAsBytesSync();
-    return _decodeString(bytes, encoding);
+    return encoding.decode(bytes);
   }
 
   static List<String> _decodeLines(List<int> bytes, Encoding encoding) {
     if (bytes.length == 0) return [];
     var list = [];
     var controller = new StreamController(sync: true);
     controller.stream
-        .transform(new StringDecoder(encoding))
+        .transform(encoding.decoder)
         .transform(new LineSplitter())
         .listen((line) => list.add(line));
     controller.add(bytes);
     controller.close();
     return list;
   }
 
-  Future<List<String>> readAsLines({Encoding encoding: Encoding.UTF_8}) {
+  Future<List<String>> readAsLines({Encoding encoding: UTF8}) {
     _ensureFileService();
     return readAsBytes().then((bytes) {
       return _decodeLines(bytes, encoding);
     });
   }
 
-  List<String> readAsLinesSync({Encoding encoding: Encoding.UTF_8}) {
+  List<String> readAsLinesSync({Encoding encoding: UTF8}) {
     return _decodeLines(readAsBytesSync(), encoding);
   }
 
   Future<File> writeAsBytes(List<int> bytes,
                             {FileMode mode: FileMode.WRITE}) {
     try {
       IOSink sink = openWrite(mode: mode);
       sink.add(bytes);
       sink.close();
       return sink.done.then((_) => this);
     } catch (e) {
       return new Future.error(e);
     }
   }
 
   void writeAsBytesSync(List<int> bytes, {FileMode mode: FileMode.WRITE}) {
     RandomAccessFile opened = openSync(mode: mode);
     opened.writeFromSync(bytes, 0, bytes.length);
     opened.closeSync();
   }
 
   Future<File> writeAsString(String contents,
                              {FileMode mode: FileMode.WRITE,
-                              Encoding encoding: Encoding.UTF_8}) {
+                              Encoding encoding: UTF8}) {
     try {
-      return writeAsBytes(_encodeString(contents, encoding), mode: mode);
+      return writeAsBytes(encoding.encode(contents), mode: mode);
     } catch (e) {
       return new Future.error(e);
     }
   }
 
   void writeAsStringSync(String contents,
                          {FileMode mode: FileMode.WRITE,
-                          Encoding encoding: Encoding.UTF_8}) {
-    writeAsBytesSync(_encodeString(contents, encoding), mode: mode);
+                          Encoding encoding: UTF8}) {
+    writeAsBytesSync(encoding.encode(contents), mode: mode);
   }
 
   String toString() => "File: '$path'";
 
   void _ensureFileService() {
     if (_fileService == null) {
       _fileService = _FileUtils._newServicePort();
     }
   }
 
@@ skipping 233 matching lines @@
     var result = _writeFrom(_id,
                             bufferAndStart.buffer,
                             bufferAndStart.start,
                             end - (start - bufferAndStart.start));
     if (result is OSError) {
       throw new FileException("writeFrom failed", path, result);
     }
   }
 
   Future<RandomAccessFile> writeString(String string,
-                                       {Encoding encoding: Encoding.UTF_8}) {
+                                       {Encoding encoding: UTF8}) {
     if (encoding is! Encoding) {
       throw new ArgumentError(encoding);
     }
-    var data = _encodeString(string, encoding);
+    var data = encoding.encode(string);
     return writeFrom(data, 0, data.length);
   }
 
-  void writeStringSync(String string, {Encoding encoding: Encoding.UTF_8}) {
+  void writeStringSync(String string, {Encoding encoding: UTF8}) {
     if (encoding is! Encoding) {
       throw new ArgumentError(encoding);
     }
-    var data = _encodeString(string, encoding);
+    var data = encoding.encode(string);
     writeFromSync(data, 0, data.length);
   }
 
   Future<int> position() {
     _ensureFileService();
     if (closed) return _closedException();
     List request = new List(2);
     request[0] = _POSITION_REQUEST;
     request[1] = _id;
     return _fileService.call(request).then((response) {
@@ skipping 127 matching lines @@
   void _checkNotClosed() {
     if (closed) {
       throw new FileException("File closed", path);
     }
   }
 
   Future _closedException() {
     return new Future.error(new FileException("File closed", path));
   }
 }