Modify tests to use Directory.systemTemp

tests/standalone/io/stream_pipe_test.dart

Index: tests/standalone/io/stream_pipe_test.dart
diff --git a/tests/standalone/io/stream_pipe_test.dart b/tests/standalone/io/stream_pipe_test.dart
index 5f0b801f334548e0ca7fed5399461926206122a8..2504e77e4f2543e260707e7baa72e6ffae96c9fd 100644
--- a/tests/standalone/io/stream_pipe_test.dart
+++ b/tests/standalone/io/stream_pipe_test.dart
@@ -67,7 +67,7 @@ testFileToFilePipe1() {
       getDataFilename("tests/standalone/io/readline_test1.dat");
   var srcStream = new File(srcFileName).openRead();
 
-  var tempDir = new Directory('').createTempSync();
+  var tempDir = Directory.systemTemp.createTempSync('dart_stream_pipe');
   String dstFileName = tempDir.path + "/readline_test1.dat";
   new File(dstFileName).createSync();
   var output = new File(dstFileName).openWrite();
@@ -93,7 +93,7 @@ testFileToFilePipe2() {
   var srcFile = new File(srcFileName);
   var srcStream = srcFile.openRead();
 
-  var tempDir = new Directory('').createTempSync();
+  var tempDir = Directory.systemTemp.createTempSync('dart_stream_pipe');
   var dstFileName = tempDir.path + "/readline_test1.dat";
   var dstFile = new File(dstFileName);
   dstFile.createSync();
@@ -135,7 +135,7 @@ testFileToFilePipe3() {
   var srcFile = new File(srcFileName);
   var srcStream = srcFile.openRead();
 
-  var tempDir = new Directory('').createTempSync();
+  var tempDir = Directory.systemTemp.createTempSync('dart_stream_pipe');
   var dstFileName = tempDir.path + "/readline_test1.dat";
   var dstFile = new File(dstFileName);
   dstFile.createSync();