Use memory compiler in compiler_helper.dart.

tests/compiler/dart2js/warnings_checker.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.
 
 // Test that dart2js produces the expected static type warnings to ensures that
 // the analyzer and dart2js agrees on the tests.
 
 import 'dart:async';
 import 'dart:io';
 import 'package:expect/expect.dart';
 import 'package:async_helper/async_helper.dart';
 import 'memory_compiler.dart';
+import 'package:compiler/src/commandline_options.dart';
 import 'package:compiler/src/filenames.dart';
 import 'package:compiler/src/io/source_file.dart';
 import 'package:compiler/src/source_file_provider.dart';
 import 'package:compiler/src/util/uri_extras.dart';
 import 'dart:convert';
 
 void checkWarnings(Map<String, dynamic> tests, [List<String> arguments]) {
   bool isWindows = Platform.isWindows;
   Uri script = currentDirectory.resolveUri(Platform.script);
   bool warningsMismatch = false;
@@ skipping 11 matching lines @@
            line.contains('static warning'))) {
         expectedWarnings[lineNo] = line;
       }
       lineNo++;
     }
     Set<int> unseenWarnings = new Set<int>.from(expectedWarnings.keys);
     DiagnosticCollector collector = new DiagnosticCollector();
     await runCompiler(
         entryPoint: uri,
         diagnosticHandler: collector,
-        options: ['--analyze-only'],
+        options: [Flags.analyzeOnly],
         showDiagnostics: verbose);
     Map<String, List<int>> statusMap = tests[test];
     // Line numbers with known unexpected warnings.
     List<int> unexpectedStatus = [];
     if (statusMap != null && statusMap.containsKey('unexpected')) {
       unexpectedStatus = statusMap['unexpected'];
     }
     // Line numbers with known missing warnings.
     List<int> missingStatus = [];
     if (statusMap != null && statusMap.containsKey('missing')) {
@@ skipping 18 matching lines @@
           String line = expectedWarnings[lineNo];
           print('$uri [${lineNo+1}]: Missing static type warning.');
           print(line);
         }
       }
     }
   }).then((_) {
     Expect.isFalse(warningsMismatch);
   }));
 }