Fix leaking FD from readAs*Sync and writeAs*Sync.

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 443 matching lines @@
           // May be character device, try to read it in chunks.
           return readDataChunked(file);
         }
         return file.read(length);
       }).whenComplete(file.close);
     });
   }
 
   List<int> readAsBytesSync() {
     var opened = openSync();
-    var data;
-    var length = opened.lengthSync();
-    if (length == 0) {
-      // May be character device, try to read it in chunks.
-      var builder = new BytesBuilder(copy: false);
-      do {
-        data = opened.readSync(_BLOCK_SIZE);
-        if (data.length > 0) builder.add(data);
-      } while (data.length == _BLOCK_SIZE);
-      data = builder.takeBytes();
-    } else {
-      data = opened.readSync(length);
+    try {
+      var data;
+      var length = opened.lengthSync();
+      if (length == 0) {
+        // May be character device, try to read it in chunks.
+        var builder = new BytesBuilder(copy: false);
+        do {
+          data = opened.readSync(_BLOCK_SIZE);
+          if (data.length > 0) builder.add(data);
+        } while (data.length == _BLOCK_SIZE);
+        data = builder.takeBytes();
+      } else {
+        data = opened.readSync(length);
+      }
+      return data;
+    } finally {
+      opened.closeSync();
     }
-    opened.closeSync();
-    return data;
   }
 
   String _tryDecode(List<int> bytes, Encoding encoding) {
     try {
       return encoding.decode(bytes);
     } catch (_) {
       throw new FileSystemException(
           "Failed to decode data using encoding '${encoding.name}'", path);
     }
   }
@@ skipping 43 matching lines @@
             return this;
           })
           .whenComplete(file.close);
     });
   }
 
   void writeAsBytesSync(List<int> bytes,
                         {FileMode mode: FileMode.WRITE,
                          bool flush: false}) {
     RandomAccessFile opened = openSync(mode: mode);
-    opened.writeFromSync(bytes, 0, bytes.length);
-    if (flush) opened.flushSync();
-    opened.closeSync();
+    try {
+      opened.writeFromSync(bytes, 0, bytes.length);
+      if (flush) opened.flushSync();
+    } finally {
+      opened.closeSync();
+    }
   }
 
   Future<File> writeAsString(String contents,
                              {FileMode mode: FileMode.WRITE,
                               Encoding encoding: UTF8,
                               bool flush: false}) {
     try {
       return writeAsBytes(encoding.encode(contents), mode: mode, flush: flush);
     } catch (e) {
       return new Future.error(e);
@@ skipping 360 matching lines @@
   void _checkAvailable() {
     if (_asyncDispatched) {
       throw new FileSystemException("An async operation is currently pending",
                                     path);
     }
     if (closed) {
       throw new FileSystemException("File closed", path);
     }
   }
 }