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

tests/standalone/http_launch_test.dart

Index: tests/standalone/http_launch_test.dart
diff --git a/tests/standalone/http_launch_test.dart b/tests/standalone/http_launch_test.dart
index cebab776a592069a5923cfbd154ae2e2212c367f..5404f0ff5877ded9fb45747b0c8a6c7c3ad29dc9 100644
--- a/tests/standalone/http_launch_test.dart
+++ b/tests/standalone/http_launch_test.dart
@@ -19,8 +19,7 @@ import 'dart:io';
 import 'package:expect/expect.dart';
 
 String pathToExecutable = Platform.executable;
-String pathOfData = new File(Platform.script).parent.path +
-                    '/http_launch_data';
+Uri pathOfData = Platform.script.resolve('http_launch_data/');
 int port;
 
 _sendNotFound(HttpResponse response) {
@@ -29,9 +28,9 @@ _sendNotFound(HttpResponse response) {
 }
 
 handleRequest(HttpRequest request) {
-  final String path = request.uri.path;
-  final String requestPath = '$pathOfData$path';
-  final File file = new File(requestPath);
+  final String path = request.uri.path.substring(1);
+  final Uri requestPath = pathOfData.resolve(path);
+  final File file = new File(requestPath.toFilePath());
   file.exists().then((bool found) {
     if (found) {
       file.openRead()
@@ -47,7 +46,8 @@ serverRunning(HttpServer server) {
   port = server.port;
   server.listen(handleRequest);
   Future<ProcessResult> no_http_run =
-      Process.run(pathToExecutable, ['${pathOfData}/http_launch_main.dart']);
+    Process.run(pathToExecutable,
+                [pathOfData.resolve('http_launch_main.dart').toFilePath()]);
   Future<ProcessResult> http_run =
     Process.run(pathToExecutable,
                 ['http://127.0.0.1:$port/http_launch_main.dart']);