Update watch docs.

sdk/lib/io/file_system_entity.dart

Index: sdk/lib/io/file_system_entity.dart
diff --git a/sdk/lib/io/file_system_entity.dart b/sdk/lib/io/file_system_entity.dart
index adf82455b3e7b5ab68eac208ac3e5fe4ba3526cb..dbad475cc05c1ee0c651d8586e9f9672a2f00f5b 100644
--- a/sdk/lib/io/file_system_entity.dart
+++ b/sdk/lib/io/file_system_entity.dart
@@ -418,6 +418,9 @@ abstract class FileSystemEntity {
    * Use `events` to specify what events to listen for. The constants in
    * [FileSystemEvent] can be or'ed together to mix events. Default is
    * [FileSystemEvent.ALL].
+   *
+   * If the system is unable to pair a move-event, the event may be rewritten

[Søren Gjesse, 2014/09/23 11:21:41]

This is a bit out of the blue. There is no mentioning of paring move events
above, so some more documentation is needed here.

[Anders Johnsen, 2014/09/23 11:30:07]

Simplified a bit - no longer any mention to how we do things.

+   * to a delete and create event.
    */
   Stream<FileSystemEvent> watch({int events: FileSystemEvent.ALL,
                                  bool recursive: false})