Use Directory.systemTemp getter in pkg subdirectory of repository.

BUG=
R=sgjesse@google.com

Review URL: https://codereview.chromium.org//25731003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart/pkg/watcher@28218 260f80e4-7a28-3924-810f-c04153c831b5

pkgs/watcher/test/utils.dart

diff --git a/pkgs/watcher/test/utils.dart b/pkgs/watcher/test/utils.dart
index 656ddf8..28d57b0 100644
--- a/pkgs/watcher/test/utils.dart
+++ b/pkgs/watcher/test/utils.dart
@@ -46,7 +46,7 @@
 ///
 /// This should usually be called by [setUp].
 void createSandbox() {
-  var dir = new Directory("").createTempSync();
+  var dir = Directory.systemTemp.createTempSync('watcher_test_');
   _sandboxDir = dir.path;
 
   _mockFileModificationTimes = new Map<String, int>();