Don't use length when reading a file in chunks (but continue to EOF).

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 53 matching lines @@
       return closeFuture;
     } else {
       return new Future.value();
     }
   }
 
   void _readBlock() {
     // Don't start a new read if one is already in progress.
     if (_readInProgress) return;
     _readInProgress = true;
-    _openedFile.length()
-      .then((length) {
-        if (_position >= length) {
-          _readInProgress = false;
+    _openedFile.read(_BLOCK_SIZE)
+      .then((block) {
+        _readInProgress = false;
+        if (block.length == 0) {
           if (!_unsubscribed) {
             _closeFile().then((_) { _controller.close(); });
             _unsubscribed = true;
           }
-          return null;
-        } else {
-          return _openedFile.read(_BLOCK_SIZE);
-        }
-      })
-      .then((block) {
-        _readInProgress = false;
-        if (block == null || _unsubscribed) {
           return;
         }
         _position += block.length;
         if (_paused) {
           _currentBlock = block;
         } else {
           _controller.add(block);
           _readBlock();
         }
       })
@@ skipping 937 matching lines @@
           new FileIOException("File closed '$_path'"));
     });
     return completer.future;
   }
 
   final String _path;
   int _id;
 
   SendPort _fileService;
 }