Change dart:io Platform.script to return a Uri.

tests/lib/mirrors/library_uri_io_test.dart

Index: tests/lib/mirrors/library_uri_io_test.dart
diff --git a/tests/lib/mirrors/library_uri_io_test.dart b/tests/lib/mirrors/library_uri_io_test.dart
index 7bc364462b545277e5bdb30f8bdb05d89f548c3a..c44ff1bad977a9814ca82f117c3a8592f61a6986 100644
--- a/tests/lib/mirrors/library_uri_io_test.dart
+++ b/tests/lib/mirrors/library_uri_io_test.dart
@@ -23,10 +23,7 @@ testLibraryUri(var value, Uri expectedUri) {
 main() {
   var mirrors = currentMirrorSystem();
   test("Test current library uri", () {
-    String appendSlash(String path) => path.endsWith('/') ? path : '$path/';
-    Uri cwd =
-        new Uri.file(appendSlash(new File('.').resolveSymbolicLinksSync()));
-    Uri uri = cwd.resolveUri(new Uri.file(Platform.script));
+    Uri uri = Uri.base.resolveUri(Platform.script);
     testLibraryUri(new Class(), uri);
   });
 }