Replace EngineTestCase.assertSize() with hasLength().

pkg/analyzer/test/generated/static_warning_code_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 engine.static_warning_code_test;
 
 import 'package:analyzer/src/generated/source_io.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/parser.dart' show ParserErrorCode;
 import 'package:unittest/unittest.dart';
@@ skipping 253 matching lines @@
 }''');
     addNamedSource("/lib2.dart", r'''
 library lib2;
 class _A {}
 g(h(_A a)) {}''');
     resolve(source);
     // The name _A is private to the library it's defined in, so this is a type mismatch.
     // Furthermore, the error message should mention both _A and the filenames
     // so the user can figure out what's going on.
     List<AnalysisError> errors = analysisContext2.computeErrors(source);
-    EngineTestCase.assertLength(1, errors);
+    expect(errors, hasLength(1));
     AnalysisError error = errors[0];
     expect(StaticWarningCode.ARGUMENT_TYPE_NOT_ASSIGNABLE, error.errorCode);
     String message = error.message;
     expect(message.indexOf("_A") != -1, isTrue);
     expect(message.indexOf("lib1.dart") != -1, isTrue);
     expect(message.indexOf("lib2.dart") != -1, isTrue);
   }
 
   void test_argumentTypeNotAssignable_annotation_namedConstructor() {
     Source source = addSource(r'''
@@ skipping 2853 matching lines @@
 }''');
     resolve(source);
     assertErrors(source, [StaticWarningCode.VOID_RETURN_FOR_GETTER]);
   }
 }
 
 main() {
   groupSep = ' | ';
   runReflectiveTests(StaticWarningCodeTest);
 }