Handle complicated imports.

pkg/front_end/lib/src/fasta/builder/prefix_builder.dart

 // Copyright (c) 2016, 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 fasta.prefix_builder;
 
 import 'builder.dart' show Builder, LibraryBuilder, MemberBuilder;
 
 import '../messages.dart' show warning;
 
@@ skipping 25 matching lines @@
       return builder.member.isInstanceMember
           ? internalError("Unexpected instance member in export scope")
           : builder.member;
     } else if (builder is MemberBuilder) {
       return builder.target;
     } else {
       return null;
     }
   }
 
-  Builder combineAmbiguousImport(
-      String name, Builder other, LibraryBuilder library) {
-    if (other is PrefixBuilder) {
-      /// Handles the case where the same prefix is used for different imports.
-      other.exports.forEach((String name, Builder member) {
-        Builder existing = exports[name];
-        if (existing != null) {
-          member = existing.combineAmbiguousImport(name, member, library);
-        }
-        exports[name] = member;
-      });
-      return this;
-    }
-    return super.combineAmbiguousImport(name, other, library);
-  }
-
   @override
   String get fullNameForErrors => name;
 }