Remove noisy warning.

pkg/front_end/lib/src/fasta/dill/dill_library_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.dill_library_builder;
 
 import 'package:kernel/ast.dart' show
     Class,
     ExpressionStatement,
     Field,
@@ skipping 71 matching lines @@
         classBulder.addMember(field);
       }
     }
   }
 
   void addMember(Member member) {
     String name = member.name.name;
     if (name == "_exports#") {
       // This is a hack / work around for storing exports in dill files. See
       // [compile_platform.dart](../compile_platform.dart).
-      print("$uri: _exports# not implemented yet.");
     } else {
       addBuilder(name, new DillMemberBuilder(member, this), member.fileOffset);
     }
   }
 
   Builder addBuilder(String name, Builder builder, int charOffset) {
     if (name == null || name.isEmpty) return null;
     members[name] = builder;
     if (!name.startsWith("_")) {
       exports[name] = builder;
     }
     return builder;
   }
 
   bool addToExportScope(String name, Builder member) {
     return internalError("Not implemented yet.");
   }
 
   void addToScope(String name, Builder member) {
     internalError("Not implemented yet.");
   }
 
   KernelInvalidTypeBuilder buildAmbiguousBuilder(
       String name, Builder builder, Builder other, int charOffset) {
     return new KernelInvalidTypeBuilder(name, charOffset, fileUri);
   }
 }