Fix a couple of doc comment references - and many spelling mistakes

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.
@@ skipping 394 matching lines @@
   final _ToEncodable _toEncodable;
   final StringConversionSink _sink;
   bool _isDone = false;
 
   _JsonEncoderSink(this._sink, this._toEncodable, this._indent);
 
   /**
    * Encodes the given object [o].
    *
    * It is an error to invoke this method more than once on any instance. While
-   * this makes the input effectly non-chunked the output will be generated in
-   * a chunked way.
+   * this makes the input effectively non-chunked the output will be generated
+   * in a chunked way.
    */
   void add(Object o) {
     if (_isDone) {
       throw new StateError("Only one call to add allowed");
     }
     _isDone = true;
     ClosableStringSink stringSink = _sink.asStringSink();
     _JsonStringStringifier.printOn(o, stringSink, _toEncodable, _indent);
     stringSink.close();
   }
@@ skipping 623 matching lines @@
         buffer.setRange(index, end, indent);
         index = end;
       } else {
         for (int i = 0; i < indentLength; i++) {
           writeByte(indent[i]);
         }
       }
     }
   }
 }