Add a note on watching files on Linux.

sdk/lib/io/file_system_entity.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;
 
 class FileSystemEntityType {
   static const FILE = const FileSystemEntityType._internal(0);
   static const DIRECTORY = const FileSystemEntityType._internal(1);
   static const LINK = const FileSystemEntityType._internal(2);
@@ skipping 331 matching lines @@
   /**
    * Start watching the [FileSystemEntity] for changes.
    *
    * The implementation uses platform-dependent event-based APIs for receiving
    * file-system notifications, thus behavior depends on the platform.
    *
    *   * `Windows`: Uses `ReadDirectoryChangesW`. The implementation only
    *     supports watching directories. Recursive watching is supported.
    *   * `Linux`: Uses `inotify`. The implementation supports watching both
    *     files and directories. Recursive watching is not supported.
+   *     Note: When watching files directly, delete events might not happen
+   *     as expected.
    *   * `Mac OS`: Uses `FSEvents`. The implementation supports watching both
    *     files and directories. Recursive watching is supported.
    *     Note: events happened slightly before calling [watch], may be part of
    *     the returned stream, on Mac OS.
    *
    * The system will start listening for events once the returned [Stream] is
    * being listened to, not when the call to [watch] is issued.
    *
    * The returned value is an endless broadcast [Stream], that only stops when
    * one of the following happends:
@@ skipping 372 matching lines @@
   }
 }
 
 
 abstract class _FileSystemWatcher {
   external factory _FileSystemWatcher(String path, int events, bool recursive);
   external static bool get isSupported;
 
   Stream<FileSystemEvent> get stream;
 }