Don't close the _FileStream until all operations are done.

sdk/lib/io/file_impl.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart.io;
 
 // Read the file in blocks of size 64k.
 const int _BLOCK_SIZE = 64 * 1024;
 
 
@@ skipping 72 matching lines @@
     // Don't start a new read if one is already in progress.
     if (_readInProgress) return;
     _readInProgress = true;
     int readBytes = _BLOCK_SIZE;
     if (_end != null) {
       readBytes = min(readBytes, _end - _position);
       if (readBytes < 0) {
         _readInProgress = false;
         if (!_unsubscribed) {
           _controller.addError(new RangeError("Bad end position: $_end"));
-          _closeFile().then((_) { _controller.close(); });
+          _closeFile();
           _unsubscribed = true;
         }
         return;
       }
     }
     _openedFile.read(readBytes)
       .whenComplete(() {
         _readInProgress = false;
       })
       .then((block) {
@@ skipping 32 matching lines @@
       _controller.addError(new RangeError("Bad start position: $_position"));
       _controller.close();
       return;
     }
     Future<RandomAccessFile> openFuture;
     if (_path != null) {
       openFuture = new File(_path).open(mode: FileMode.READ);
     } else {
       openFuture = new Future.value(_File._openStdioSync(0));
     }
+    _readInProgress = true;
     openFuture
       .then((RandomAccessFile opened) {
         _openedFile = opened;
         if (_position > 0) {
           return opened.setPosition(_position);
         }
       })
+      .whenComplete(() {
+        _readInProgress = false;
+      })
       .then((_) => _readBlock())
       .catchError((e) {
         _controller.addError(e);
-        _controller.close();
+        _closeFile();
       });
   }
 
   void _resume() {
     _paused = false;
     if (_currentBlock != null) {
       _controller.add(_currentBlock);
       _currentBlock = null;
     }
     // Resume reading unless we are already done.
@@ skipping 702 matching lines @@
 
   void _checkAvailable() {
     if (_asyncDispatched) {
       throw new FileSystemException("An async operation is currently pending", path);
     }
     if (closed) {
       throw new FileSystemException("File closed", path);
     }
   }
 }