Fix warnings and hints in the SDK

sdk/lib/io/http_parser.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.io;
 
 // Global constants.
 class _Const {
   // Bytes for "HTTP".
   static const HTTP = const [72, 84, 84, 80];
@@ skipping 938 matching lines @@
 
   // expected should already be lowercase.
   bool _caseInsensitiveCompare(List<int> expected, List<int> value) {
     if (expected.length != value.length) return false;
     for (int i = 0; i < expected.length; i++) {
       if (expected[i] != _toLowerCaseByte(value[i])) return false;
     }
     return true;
   }
 
-  int _expect(int val1, int val2) {
+  void _expect(int val1, int val2) {
     if (val1 != val2) {
       throw new HttpException("Failed to parse HTTP");
     }
   }
 
   int _expectHexDigit(int byte) {
     if (0x30 <= byte && byte <= 0x39) {
       return byte - 0x30;  // 0 - 9
     } else if (0x41 <= byte && byte <= 0x46) {
       return byte - 0x41 + 10;  // A - F
@@ skipping 69 matching lines @@
     }
   }
 
   void _reportError(error, [stackTrace]) {
     if (_socketSubscription != null) _socketSubscription.cancel();
     _state = _State.FAILURE;
     _controller.addError(error, stackTrace);
     _controller.close();
   }
 }