Made old dart:json library use convert to parse JSON.

sdk/lib/convert/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.convert;
 
 /**
+ * Error thrown by JSON serialization if an object cannot be serialized.
+ *
+ * The [unsupportedObject] field holds that object that failed to be serialized.
+ *
+ * If an object isn't directly serializable, the serializer calls the 'toJson'
+ * method on the object. If that call fails, the error will be stored in the
+ * [cause] field. If the call returns an object that isn't directly
+ * serializable, the [cause] is be null.
+ */
+class JsonUnsupportedObjectError extends Error {
+  /** The object that could not be serialized. */
+  final unsupportedObject;
+  /** The exception thrown by object's [:toJson:] method, if any. */
+  final cause;
+
+  JsonUnsupportedObjectError(this.unsupportedObject, { this.cause });
+
+  String toString() {
+    if (cause != null) {
+      return "Calling toJson method on object failed.";
+    } else {
+      return "Object toJson method returns non-serializable value.";
+    }
+  }
+}
+
+
+/**
+ * Reports that an object could not be stringified due to cyclic references.
+ *
+ * An object that references itself cannot be serialized by [stringify].
+ * When the cycle is detected, a [JsonCyclicError] is thrown.
+ */
+class JsonCyclicError extends JsonUnsupportedObjectError {
+  /** The first object that was detected as part of a cycle. */
+  JsonCyclicError(Object object): super(object);
+  String toString() => "Cyclic error in JSON stringify";
+}
+
+
+/**
  * An instance of the default implementation of the [JsonCodec].
  *
  * This instance provides a convenient access to the most common JSON
  * use cases.
  *
  * Examples:
  *
  *     var encoded = JSON.encode([1, 2, { "a": null }]);
  *     var decoded = JSON.decode('["foo", { "bar": 499 }]');
  */
@@ skipping 156 matching lines @@
    * JSON values.
    *
    * If `this` was initialized with a reviver, then the parsing operation
    * invokes the reviver on every object or list property that has been parsed.
    * The arguments are the property name ([String]) or list index ([int]), and
    * the value is the parsed value. The return value of the reviver is used as
    * the value of that property instead the parsed value.
    *
    * Throws [FormatException] if the input is not valid JSON text.
    */
-  Object convert(String input) => OLD_JSON_LIB.parse(input, _reviver);
+  Object convert(String input) => _parseJson(input, _reviver);
 
   /**
    * Starts a conversion from a chunked JSON string to its corresponding
    * object.
    *
    * The output [sink] receives exactly one decoded element through `add`.
    */
   StringConversionSink startChunkedConversion(
       ChunkedConversionSink<Object> sink) {
     return new _JsonDecoderSink(_reviver, sink);
@@ skipping 15 matching lines @@
   final ChunkedConversionSink<Object> _chunkedSink;
 
   _JsonDecoderSink(this._reviver, this._chunkedSink)
       : super(new StringBuffer());
 
   void close() {
     super.close();
     StringBuffer buffer = _stringSink;
     String accumulated = buffer.toString();
     buffer.clear();
-    Object decoded = OLD_JSON_LIB.parse(accumulated, _reviver);
+    Object decoded = _parseJson(accumulated, _reviver);
     _chunkedSink.add(decoded);
     _chunkedSink.close();
   }
 }
+
+// Internal optimized JSON parsing implementation.
+external _parseJson(String source, reviver(key, value));