Don't report file-system move events on Mac OS, and use no-defer to avoid past events.

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 81d406dcd4e849f30cfdf471b0840dbb7c7adfbc..896ef263d3391d452a95f2795f213da3d982d6eb 100644
--- a/sdk/lib/io/file_system_entity.dart
+++ b/sdk/lib/io/file_system_entity.dart
@@ -353,8 +353,6 @@ abstract class FileSystemEntity {
    *     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.