Ensure locations are always provided, but don't store them yet.

pkg/kernel/lib/ast.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.
 
 /// -----------------------------------------------------------------------
 ///                           ERROR HANDLING
 /// -----------------------------------------------------------------------
 ///
 /// As a rule of thumb, errors that can be detected statically are handled by
 /// the frontend, typically by translating the erroneous code into a 'throw' or
@@ skipping 170 matching lines @@
   String name;
   final List<Class> classes;
   final List<Procedure> procedures;
   final List<Field> fields;
 
   Library(this.importUri,
       {this.name,
       this.isExternal: false,
       List<Class> classes,
       List<Procedure> procedures,
-      List<Field> fields})
+      List<Field> fields,
+      this.fileUri})
       : this.classes = classes ?? <Class>[],
         this.procedures = procedures ?? <Procedure>[],
         this.fields = fields ?? <Field>[] {
     setParents(this.classes, this);
     setParents(this.procedures, this);
     setParents(this.fields, this);
   }
 
   /// Returns the top-level fields and procedures defined in this library.
   ///
@@ skipping 3466 matching lines @@
     }
   }
 }
 
 class Source {
   final List<int> lineStarts;
   final String source;
 
   Source(this.lineStarts, this.source);
 }