Don't test for file differences in the polling watcher.

The non-polling forms don't do this, so this makes the polling
style behave the same. It also has two important benefits:

1. On Windows, this avoids opening the files being watched.
   Since opening a file prevents it from being deleted on
   Windows, this causes the watcher to interfere with the
   files and leads to some flaky tests and buggy user
   behavior.

2. It saves some time and memory since we don't need to store
   the SHA1 for every file being watched.

BUG=http://dartbug.com/13026, http://dartbug.com/15431
R=nweiz@google.com

Review URL: https://codereview.chromium.org//122573003

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart/pkg/watcher@31574 260f80e4-7a28-3924-810f-c04153c831b5
6 files changed
tree: 056a82cfa215ea7f3ba440110d847b95e9c6ae43
  1. example/
  2. lib/
  3. test/
  4. pubspec.yaml
  5. 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.