Fix build for throwsStateError: remove duplicate definitions in other tests.

pkg/http/test/utils.dart

 // Copyright (c) 2012, 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.
 
 library test_utils;
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:json' as json;
 import 'dart:uri';
@@ skipping 120 matching lines @@
 
     return _matcher.matches(parsed, matchState);
   }
 
   Description describe(Description description) {
     return description.add('parses to a value that ')
       .addDescriptionOf(_matcher);
   }
 }
 
-// TODO(nweiz): remove this once it's built in to unittest (issue 7922).
-/// A matcher for StateErrors.
-const isStateError = const _StateError();
-
-/// A matcher for functions that throw StateError.
-const Matcher throwsStateError =
-    const Throws(isStateError);
-
-class _StateError extends TypeMatcher {
-  const _StateError() : super("StateError");
-  bool matches(item, MatchState matchState) => item is StateError;
-}
-
 /// A matcher for HttpExceptions.
 const isHttpException = const _HttpException();
 
 /// A matcher for functions that throw HttpException.
 const Matcher throwsHttpException =
     const Throws(isHttpException);
 
 class _HttpException extends TypeMatcher {
   const _HttpException() : super("HttpException");
   bool matches(item, MatchState matchState) => item is HttpException;
@@ skipping 19 matching lines @@
 const isSocketIOException = const _SocketIOException();
 
 /// A matcher for functions that throw SocketIOException.
 const Matcher throwsSocketIOException =
     const Throws(isSocketIOException);
 
 class _SocketIOException extends TypeMatcher {
   const _SocketIOException() : super("SocketIOException");
   bool matches(item, MatchState matchState) => item is SocketIOException;
 }