Enable inference in the core libs

test/dart_codegen/expect/convert/utf.dart

 part of dart.convert;
  const int UNICODE_REPLACEMENT_CHARACTER_RUNE = 0xFFFD;
  const int UNICODE_BOM_CHARACTER_RUNE = 0xFEFF;
  const Utf8Codec UTF8 = const Utf8Codec();
  class Utf8Codec extends Encoding {final bool _allowMalformed;
  const Utf8Codec({
   bool allowMalformed : false}
 ) : _allowMalformed = allowMalformed;
  String get name => "utf-8";
  String decode(List<int> codeUnits, {
@@ skipping 33 matching lines @@
  Stream<List<int>> bind(Stream<String> stream) => ((__x32) => DEVC$RT.cast(__x32, DEVC$RT.type((DDC$async$.Stream<dynamic> _) {
 }
 ), DEVC$RT.type((DDC$async$.Stream<List<int>> _) {
 }
 ), "CastDynamic", """line 129, column 52 of dart:convert/utf.dart: """, __x32 is DDC$async$.Stream<List<int>>, false))(super.bind(stream));
 }
  class _Utf8Encoder {int _carry = 0;
  int _bufferIndex = 0;
  final List<int> _buffer;
  static const _DEFAULT_BYTE_BUFFER_SIZE = 1024;
- _Utf8Encoder() : this.withBufferSize(DEVC$RT.cast(_DEFAULT_BYTE_BUFFER_SIZE, dynamic, int, "CastGeneral", """line 143, column 40 of dart:convert/utf.dart: """, _DEFAULT_BYTE_BUFFER_SIZE is int, true));
+ _Utf8Encoder() : this.withBufferSize(_DEFAULT_BYTE_BUFFER_SIZE);
  _Utf8Encoder.withBufferSize(int bufferSize) : _buffer = _createBuffer(bufferSize);
  static List<int> _createBuffer(int size) => new Uint8List(size);
  bool _writeSurrogate(int leadingSurrogate, int nextCodeUnit) {
 if (_isTailSurrogate(nextCodeUnit)) {
 int rune = _combineSurrogatePair(leadingSurrogate, nextCodeUnit);
  assert (rune > _THREE_BYTE_LIMIT); assert (rune <= _FOUR_BYTE_LIMIT); _buffer[_bufferIndex++] = 0xF0 | (rune >> 18);
  _buffer[_bufferIndex++] = 0x80 | ((rune >> 12) & 0x3f);
  _buffer[_bufferIndex++] = 0x80 | ((rune >> 6) & 0x3f);
  _buffer[_bufferIndex++] = 0x80 | (rune & 0x3f);
  return true;
@@ skipping 250 matching lines @@
 }
  break loop;
 }
  if (expectedUnits > 0) {
 _value = value;
  _expectedUnits = expectedUnits;
  _extraUnits = extraUnits;
 }
 }
 }