Make dart:convert strong mode clean.

sdk/lib/convert/string_conversion.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;
 
 /**
  * This class provides an interface for converters to
  * efficiently transmit String data.
  *
  * Instead of limiting the interface to one non-chunked String it accepts
  * partial strings or can be transformed into a byte sink that
  * accepts UTF-8 code units.
  *
  * This abstract class will likely get more methods over time. Implementers are
  * urged to extend [StringConversionSinkBase] or to mix in
  * [StringConversionSinkMixin], to ensure that their class covers the newly
  * added methods.
  */
-abstract class StringConversionSink
-    extends ChunkedConversionSink<String> {
+abstract class StringConversionSink extends ChunkedConversionSink<String> {
   StringConversionSink();
   factory StringConversionSink.withCallback(void callback(String accumulated))
       = _StringCallbackSink;
   factory StringConversionSink.from(Sink<String> sink)
       = _StringAdapterSink;
 
   /**
    * Creates a new instance wrapping the given [sink].
    *
    * Every string that is added to the returned instance is forwarded to
@@ skipping 302 matching lines @@
     _decoder.convert(chunk, startIndex, endIndex);
     if (_buffer.isNotEmpty) {
       String accumulated = _buffer.toString();
       _chunkedSink.addSlice(accumulated, 0, accumulated.length, isLast);
       _buffer.clear();
       return;
     }
     if (isLast) close();
   }
 }