Make FileInputStream and FileOutputStream actually asynchronous.

tests/standalone/src/StreamPipeTest.dart

Index: tests/standalone/src/StreamPipeTest.dart
diff --git a/tests/standalone/src/StreamPipeTest.dart b/tests/standalone/src/StreamPipeTest.dart
index 0a313d721c7516ae60b2c37531c2308fe7fe931b..8952777b64bee684514cd7045387a7d9e19eb41f 100644
--- a/tests/standalone/src/StreamPipeTest.dart
+++ b/tests/standalone/src/StreamPipeTest.dart
@@ -198,22 +198,24 @@ testFileToFilePipe2() {
   srcStream.closeHandler = () {
     dstStream.write([32]);
     dstStream.close();
-    var src = srcFile.openSync();
-    var dst = dstFile.openSync();
-    var srcLength = src.lengthSync();
-    var dstLength = dst.lengthSync();
-    Expect.equals(srcLength + 1, dstLength);
-    Expect.isTrue(compareFileContent(srcFileName,
-                                     dstFileName,
-                                     count: srcLength));
-    dst.setPositionSync(srcLength);
-    var data = new List<int>(1);
-    var read2 = dst.readListSync(data, 0, 1);
-    Expect.equals(32, data[0]);
-    src.closeSync();
-    dst.closeSync();
-    dstFile.deleteSync();
-    tempDir.deleteSync();
+    dstStream.closeHandler = () {
+      var src = srcFile.openSync();
+      var dst = dstFile.openSync();
+      var srcLength = src.lengthSync();
+      var dstLength = dst.lengthSync();
+      Expect.equals(srcLength + 1, dstLength);
+      Expect.isTrue(compareFileContent(srcFileName,
+                                       dstFileName,
+                                       count: srcLength));
+      dst.setPositionSync(srcLength);
+      var data = new List<int>(1);
+      var read2 = dst.readListSync(data, 0, 1);
+      Expect.equals(32, data[0]);
+      src.closeSync();
+      dst.closeSync();
+      dstFile.deleteSync();
+      tempDir.deleteSync();
+    };
   };
 
   srcStream.pipe(dstStream, close: false);