Use the correct URI for diagnostics during outline construction.

pkg/front_end/lib/src/fasta/source/outline_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.outline_builder;
 
 import 'package:kernel/ast.dart' show
     AsyncMarker,
     ProcedureKind;
 
@@ skipping 72 matching lines @@
 
   final bool isDartLibrary;
 
   String nativeMethodName;
 
   OutlineBuilder(SourceLibraryBuilder library)
       : library = library,
         isDartLibrary = library.uri.scheme == "dart";
 
   @override
-  Uri get uri => library.uri;
+  Uri get uri => library.fileUri;
 
   @override
   void endMetadata(Token beginToken, Token periodBeforeName, Token endToken) {
     debugEvent("Metadata");
     List arguments = pop();
     String postfix = popIfNotNull(periodBeforeName);
     List<TypeBuilder> typeArguments = pop();
     if (arguments == null) {
       String expression = pop();
       push(new MetadataBuilder.fromExpression(expression, postfix, library,
@@ skipping 520 matching lines @@
   Link<Token> handleMemberName(Link<Token> identifiers) {
     if (!isDartLibrary || identifiers.isEmpty) return identifiers;
     return removeNativeClause(identifiers);
   }
 
   @override
   void debugEvent(String name) {
     // printEvent(name);
   }
 }