Remove dart:codec and move classes into dart:convert.

sdk/lib/codec/json.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.codec;
-
-final JSON = new JsonCodec();
-
-/**
- * A [JsonCodec] encodes JSON objects to strings and decodes strings to
- * JSON objects.
- */
-class JsonCodec extends Codec<Object, String> {
-  const JsonCodec();
-
-  /**
-   * Creates a `JsonCodec` with the given reviver.
-   *
-   * The [reviver] function is called once for each object or list property
-   * that has been parsed during decoding. The `key` argument is either the
-   * integer list index for a list property, the map string for object
-   * properties, or `null` for the final result.
-   */
-  factory JsonCodec.withReviver(reviver(var key, var value)) =
-      _ReviverJsonCodec;
-
-  /**
-   * Parses the string and returns the resulting Json object.
-   *
-   * The optional [reviver] function, if provided, is called once for each
-   * object or list property parsed.
-   */
-  Object decode(String str, {reviver(var key, var value)}) {
-    return new JsonDecoder(reviver).convert(str);
-  }
-
-  JsonEncoder get encoder => new JsonEncoder();
-  JsonDecoder get decoder => new JsonDecoder(null);
-}
-
-class _ReviverJsonCodec extends JsonCodec {
-  final Function _reviver;
-  _ReviverJsonCodec(this._reviver);
-
-  Object decode(String str, {reviver(var key, var value)}) {
-    if (reviver == null) reviver = _reviver;
-    return new JsonDecoder(reviver).convert(str);
-  }
-
-  JsonDecoder get decoder => new JsonDecoder(_reviver);
-}