[Effen] Tapping on a menu while it's closing should not make it instantly disappear.

sky/framework/components/popup_menu.dart

Index: sky/framework/components/popup_menu.dart
diff --git a/sky/framework/components/popup_menu.dart b/sky/framework/components/popup_menu.dart
index 19b47df14e689236a287efb5e85f7917eef6c6ca..e91a4301f43e4df85d14fc627b2477a8ccb3b5f7 100644
--- a/sky/framework/components/popup_menu.dart
+++ b/sky/framework/components/popup_menu.dart
@@ -17,20 +17,37 @@ const double _kMenuOpenDuration = 300.0;
 const double _kMenuCloseDuration = 200.0;
 const double _kMenuCloseDelay = 100.0;
 
+enum MenuState { Hidden, Opening, Open, Closing }
+
 class PopupMenuController {
-  bool isOpen = false;
   AnimatedValue position = new AnimatedValue(0.0);
+  MenuState _state = MenuState.Hidden;
+  MenuState get state => _state;
+
+  bool get canReact => (_state == MenuState.Opening) || (_state == MenuState.Open);
 
-  void open() {
-    isOpen = true;
-    position.animateTo(1.0, _kMenuOpenDuration);
+  open() async {
+    if (_state != MenuState.Hidden)
+      return;
+    _state = MenuState.Opening;
+    if (await position.animateTo(1.0, _kMenuOpenDuration) == 1.0)
+      _state = MenuState.Open;
   }
 
-  Future close() {
-    return position.animateTo(0.0, _kMenuCloseDuration,
-        initialDelay: _kMenuCloseDelay).then((_) {
-      isOpen = false;
-    });
+  Future _closeState;
+  close() async {
+    var result = new Completer();
+    _closeState = result.future;
+    if ((_state == MenuState.Opening) || (_state == MenuState.Open)) {
+      _state = MenuState.Closing;
+      await position.animateTo(0.0, _kMenuCloseDuration, initialDelay: _kMenuCloseDelay);
+      _state = MenuState.Hidden;
+      _closeState = null;
+      result.complete();
+      return;
+    }
+    assert(_closeState != null);
+    return _closeState;
   }
 }