Add missing return to fix analysis (dart-lang/watcher#62)

* Add missing return to fix analysis

* address comment

* Update async_queue.dart

pkgs/watcher/CHANGELOG.md

@@ -1,3 +1,7 @@
+# 0.9.7+11
+
+* Fix an analysis hint.
+
 # 0.9.7+10
 
 * Set max SDK version to `<3.0.0`, and adjust other dependencies.

pkgs/watcher/lib/src/async_queue.dart

@@ -59,12 +59,13 @@ class AsyncQueue<T> {
   /// the process was cancelled.
   Future _processNextItem() {
     var item = _items.removeFirst();
-    return _processor(item).then((_) {
-      if (_items.isNotEmpty) return _processNextItem();
+    return _processor(item).then((_) async {
+      if (_items.isNotEmpty) return await _processNextItem();
 
       // We have drained the queue, stop processing and wait until something
       // has been enqueued.
       _isProcessing = false;
+      return null;
     });
   }
 }

pkgs/watcher/pubspec.yaml

@@ -1,5 +1,5 @@
 name: watcher
-version: 0.9.7+10
+version: 0.9.7+11
 
 description: >
   A file system watcher. It monitors changes to contents of directories and