Implement line and column numbers.

pkg/front_end/lib/src/fasta/target_implementation.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.target_implementation;
 
 import 'package:kernel/target/vm.dart' show
     VmTarget;
 
 import 'builder/builder.dart' show
@@ skipping 55 matching lines @@
     if (cachedNativeAnnotation != null) return cachedNativeAnnotation;
     LibraryBuilder internal = loader.read(Uri.parse("dart:_internal"));
     return cachedNativeAnnotation = internal.getConstructor("ExternalName");
   }
 
   void loadExtraRequiredLibraries(Loader loader) {
     for (String uri in new VmTarget(null).extraRequiredLibraries) {
       loader.read(Uri.parse(uri));
     }
   }
+
+  void addLineStarts(Uri uri, List<int> lineStarts);
 }