Prevent creation of additional FileMode and Encoding objects

runtime/bin/input_stream.dart

 // 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.
 
 /**
  * Basic input stream which supplies binary data.
  *
  * Input streams are used to read data sequentially from some data
  * source. All input streams are non-blocking. They each have a number
  * of read calls which will always return without any IO related
@@ skipping 86 matching lines @@
    */
   void set onError(void callback());
 }
 
 
 /**
  * String encodings supported by [StringInputStream] and
  * [StringOutputStream].
  */
 class Encoding {
-  static final Encoding UTF_8 = const Encoding("UTF-8");
-  static final Encoding ISO_8859_1 = const Encoding("ISO-8859-1");
-  static final Encoding ASCII = const Encoding("ASCII");
-  const Encoding(String this.name);
+  static final Encoding UTF_8 = const Encoding._internal("UTF-8");
+  static final Encoding ISO_8859_1 = const Encoding._internal("ISO-8859-1");
+  static final Encoding ASCII = const Encoding._internal("ASCII");
+  const Encoding._internal(String this.name);
   final String name;
 }
 
 
 /**
  * A string input stream wraps a basic input stream and supplies
  * string data. This data can be read either as string chunks or as
  * lines separated by line termination character sequences.
  */
 interface StringInputStream default _StringInputStream {
@@ skipping 119 matching lines @@
   void set onError(void callback());
 }
 
 
 class StreamException implements Exception {
   const StreamException([String this.message = ""]);
   const StreamException.streamClosed() : message = "Stream closed";
   String toString() => "StreamException: $message";
   final String message;
 }