Add a function to pub for finding the canonical path of a file.

sdk/lib/_internal/pub/test/test_pub.dart

 // Copyright (c) 2013, 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.
 
 /// Test infrastructure for testing pub. Unlike typical unit tests, most pub
 /// tests are integration tests that stage some stuff on the file system, run
 /// pub, and then validate the results. This library provides an API to build
 /// tests like that.
 library test_pub;
 
@@ skipping 337 matching lines @@
 
   ensureDir(pathInSandbox(appPath));
 
   // Find a Dart executable we can use to spawn. Use the same one that was
   // used to run this script itself.
   var dartBin = new Options().executable;
 
   // If the executable looks like a path, get its full path. That way we
   // can still find it when we spawn it with a different working directory.
   if (dartBin.contains(Platform.pathSeparator)) {
-    dartBin = new File(dartBin).fullPathSync();
+    dartBin = path.absolute(dartBin);
   }
 
   // Find the main pub entrypoint.
   var pubPath = path.join(testDirectory, '..', 'bin', 'pub.dart');
 
   var dartArgs = ['--package-root=$_packageRoot/', '--checked', pubPath,
       '--trace'];
   dartArgs.addAll(args);
 
   if (tokenEndpoint == null) tokenEndpoint = new Future.value();
@@ skipping 242 matching lines @@
   bool matches(item, MatchState matchState) {
     if (item is! Pair) return false;
     return _firstMatcher.matches(item.first, matchState) &&
         _lastMatcher.matches(item.last, matchState);
   }
 
   Description describe(Description description) {
     description.addAll("(", ", ", ")", [_firstMatcher, _lastMatcher]);
   }
 }