Store library paths relative to a given application root folder.

pkg/front_end/tool/perf.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.
 
 /// An entrypoint used to run portions of front_end and measure its performance.
 library front_end.tool.perf;
 
 import 'dart:async';
 import 'dart:io' show exit, stderr;
 
@@ skipping 223 matching lines @@
 
 // TODO(sigmund): replace this once kernel is produced by the frontend directly.
 Future<Program> generateKernel(Uri entryUri) async {
   var dartkTimer = new Stopwatch()..start();
   var options = new DartOptions(strongMode: false, sdk: 'sdk');
   var packages =
       await createPackages(options.packagePath, discoveryPath: entryUri.path);
   var repository = new Repository();
   DartLoader loader = new DartLoader(repository, options, packages);
 
-  Program program = loader.loadProgram(entryUri.path);
+  Program program = loader.loadProgram(entryUri);
   List errors = loader.errors;
   if (errors.isNotEmpty) {
     const int errorLimit = 100;
     stderr.writeln(errors.take(errorLimit).join('\n'));
     if (errors.length > errorLimit) {
       stderr.writeln('[error] ${errors.length - errorLimit} errors not shown');
     }
   }
   dartkTimer.stop();
   report("kernel_gen_e2e", dartkTimer.elapsedMicroseconds);
   return program;
 }