Re-land of CL 2990703002, adding fixes to analyzer_test and error_test.

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 analyzer.test.generated.static_warning_code_test;
 
 import 'package:analyzer/error/error.dart';
 import 'package:analyzer/src/error/codes.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source_io.dart';
@@ skipping 3713 matching lines @@
     await computeAnalysisResult(source);
     assertErrors(source, [StaticTypeWarningCode.UNDEFINED_SETTER]);
   }
 
   test_voidReturnForGetter() async {
     Source source = addSource(r'''
 class S {
   void get value {}
 }''');
     await computeAnalysisResult(source);
-    assertErrors(source, [StaticWarningCode.VOID_RETURN_FOR_GETTER]);
+    assertNoErrors(source);
   }
 }