Stop using pkg/matcher in JSON pretty test

tests/lib/convert/json_pretty_test.dart

 // Copyright (c) 2014, 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 json_pretty_test;
 
 import 'dart:convert';
 
-import 'package:matcher/matcher.dart';
+import "package:expect/expect.dart";
 
 void _testIndentWithNullChar() {
   var encoder = const JsonEncoder.withIndent('\x00');
   var encoded = encoder.convert([[],[[]]]);
-  expect(encoded, "[\n\x00[],\n\x00[\n\x00\x00[]\n\x00]\n]");
+  Expect.equals("[\n\x00[],\n\x00[\n\x00\x00[]\n\x00]\n]", encoded);
 }
 
 void main() {
   _testIndentWithNullChar();
 
   _expect(null, 'null');
 
   _expect([[],[[]]], '''
 [
   [],
@@ skipping 59 matching lines @@
       "bar.dart"
     ]
   }
 ]''');
 }
 
 void _expect(Object object, String expected) {
   var encoder = const JsonEncoder.withIndent('  ');
   var prettyOutput = encoder.convert(object);
 
-  expect(prettyOutput, expected);
+  Expect.equals(expected, prettyOutput);
 
   encoder = const JsonEncoder.withIndent('');
 
   var flatOutput = encoder.convert(object);
 
   var flatExpected = const LineSplitter().convert(expected)
       .map((line) => line.trimLeft())
       .join('\n');
 
-  expect(flatOutput, flatExpected);
+  Expect.equals(flatExpected, flatOutput);
 
   var compactOutput = JSON.encode(object);
 
   encoder = const JsonEncoder.withIndent(null);
-  expect(encoder.convert(object), compactOutput);
+  Expect.equals(compactOutput, encoder.convert(object));
 
   var prettyDecoded = JSON.decode(prettyOutput);
 
-  expect(JSON.encode(prettyDecoded), compactOutput);
+  Expect.equals(compactOutput, JSON.encode(prettyDecoded));
 }