Stop supporting map literals with 1 type argument

sdk/lib/_internal/compiler/implementation/dart_backend/renamer.dart

 // Copyright (c) 2012, 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.
 
 part of dart_backend;
 
 Function get _compareNodes =>
     compareBy((n) => n.getBeginToken().charOffset);
 
 typedef String _Renamer(Renamable renamable);
@@ skipping 136 matching lines @@
       final prefix =
           imports.putIfAbsent(library, () => generateUniqueName('p'));
       return '$prefix.$originalName';
     }
 
     return rename(library, originalName);
   };
 
   Function makeRenamer(generateUniqueName) =>
       (library, originalName) =>
-          renamed.putIfAbsent(library, () => <String>{})
+          renamed.putIfAbsent(library, () => <String, String>{})
               .putIfAbsent(originalName,
                   () => generateUniqueName(originalName));
 
   // Renamer function that takes library and original name and returns a new
   // name for given identifier.
   Function rename;
   Function renameElement;
   // A function that takes original identifier name and generates a new unique
   // identifier.
   Function generateUniqueName;
@@ skipping 181 matching lines @@
     index ~/= firstCharAlphabet.length;
     int length = otherCharsAlphabet.length;
     while (index >= length) {
       resultBuilder.add(otherCharsAlphabet[index % length]);
       index ~/= length;
     }
     resultBuilder.add(otherCharsAlphabet[index]);
     return resultBuilder.toString();
   }
 }