Avoid race in _FileSystemWatcher if subscription closed while event queued.

Avoid race in _FileSystemWatcher if subscription closed while event queued.

BUG=dartbug.com/22769
R=ajohnsen@google.com, sgjesse@google.com

Committed: https://code.google.com/p/dart/source/detail?r=44459

[Paul Berry, 2015-03-12 21:45:38]

paulberry@google.com changed reviewers:
+ ajohnsen@google.com

[Anders Johnsen, 2015-03-13 07:50:00]

LGTM! Thank you for tracking this down!

[Søren Gjesse, 2015-03-13 12:18:00]

sgjesse@google.com changed reviewers:
+ sgjesse@google.com

[Søren Gjesse, 2015-03-13 12:18:00]

lgtm for the fix.

https://codereview.chromium.org/1006683002/diff/1/runtime/bin/file_patch.dart
File runtime/bin/file_patch.dart (right):

https://codereview.chromium.org/1006683002/diff/1/runtime/bin/file_patch.dart...
runtime/bin/file_patch.dart:196: if (!_idMap.containsKey(pathId)) {
I am not sure this is 100% safe, but I have not scrutinized the code.

The pathId is something returned from an OS call (on Linux that is returned from
inotify_add_watch). This id can be reused, so if unwatching something and then
watching something new the OS can reuse the id.

Can this result in events for the first registration being reported on the new
one?

[Paul Berry, 2015-03-13 12:53:27]

Committed patchset #1 (id:1) manually as 44459 (presubmit successful).