add --x-package-warnings-prefix option to dartanalyzer

pkg/analyzer_cli/test/perf_report_test.dart

 // Copyright (c) 2015, 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 analyzer_cli.test.perf_report;
 
 import 'dart:convert' show JSON;
 
 import 'package:analyzer_cli/src/options.dart';
 import 'package:analyzer_cli/src/perf_report.dart';
 import 'package:unittest/unittest.dart';
+import 'package:analyzer/src/generated/engine.dart';
 
 main() {
   test('makePerfReport', () {
     var options = CommandLineOptions.parse(["somefile.dart"]);
-    var encoded = makePerfReport(1000, 1234, options);
+    var context = AnalysisEngine.instance.createAnalysisContext();
+    var encoded = makePerfReport(1000, 1234, options, context);
 
     var json = JSON.decode(encoded);
     expect(json['totalElapsedTime'], 234);
     expect(json['options']['sourceFiles'], ["somefile.dart"]);
   });
 }