Use 'Directory.watch' on Windows in pkg/watcher, instead of pooling.

This is a close copy of MacOS, except for the special handling on mac, and the extra watcher on Windows for detecting if the watched folder is deleted.

BUG=https://code.google.com/p/dart/issues/detail?id=14428,https://code.google.com/p/dart/issues/detail?id=18108,http://code.google.com/p/dart/issues/detail?id=19189
R=kasperl@google.com, sgjesse@google.com

Review URL: https://codereview.chromium.org//312743002

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart/pkg/watcher@36988 260f80e4-7a28-3924-810f-c04153c831b5
4 files changed
tree: 4c9b460706a1a5c0f8bf1bb7669d3877f2605194
  1. example/
  2. lib/
  3. test/
  4. LICENSE
  5. pubspec.yaml
  6. README.md
README.md

A file watcher. It monitors (currently by polling) for changes to contents of directories and notifies you when files have been added, removed, or modified.