More strong mode fixes for analyzer

pkg/analyzer/test/source/package_map_resolver_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.source.package_map_resolver_test;
 
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/source/package_map_resolver.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:path/path.dart';
 import 'package:unittest/unittest.dart';
 
 import '../reflective_tests.dart';
 import '../utils.dart';
 
 main() {
   initializeTestEnvironment();
   runReflectiveTests(_PackageMapUriResolverTest);
 }
 
 @reflectiveTest
 class _PackageMapUriResolverTest {
-  static const Map EMPTY_MAP = const <String, List<Folder>>{};
+  static const Map<String, List<Folder>> EMPTY_MAP =
+      const <String, List<Folder>>{};
   MemoryResourceProvider provider = new MemoryResourceProvider();
 
   void test_isPackageUri() {
     Uri uri = Uri.parse('package:test/test.dart');
     expect(uri.scheme, 'package');
     expect(PackageMapUriResolver.isPackageUri(uri), isTrue);
   }
 
   void test_isPackageUri_null_scheme() {
     Uri uri = Uri.parse('foo.dart');
@@ skipping 193 matching lines @@
     // for the file path (/foo2/bar2) is longer than pkg2's match (/foo2).
     Source source2 = _createFileSource(file2);
     Uri uri2 = resolver.restoreAbsolute(source2);
     expect(uri2.toString(), 'package:pkg1/lib.dart');
   }
 
   Source _createFileSource(String path) {
     return new NonExistingSource(path, toUri(path), UriKind.FILE_URI);
   }
 }