Fixes bug in handling restacking because of transients

ui/wm/core/transient_window_manager.cc

Index: ui/wm/core/transient_window_manager.cc
diff --git a/ui/wm/core/transient_window_manager.cc b/ui/wm/core/transient_window_manager.cc
index dc6070f8c3d63301e78ace540c1c39a915ab3522..3008853bf2844c22f672713162ff50c84041f2cc 100644
--- a/ui/wm/core/transient_window_manager.cc
+++ b/ui/wm/core/transient_window_manager.cc
@@ -137,7 +137,15 @@ void TransientWindowManager::RestackTransientDescendants() {
       base::AutoReset<Window*> resetter(
           &descendant_manager->stacking_target_,
           window_);
+      for (aura::client::TransientWindowClientObserver& observer :
+           TransientWindowController::Get()->observers_) {
+        observer.OnWillRestackTransientChildAbove(window_, *it);
+      }
       parent->StackChildAbove((*it), window_);
+      for (aura::client::TransientWindowClientObserver& observer :
+           TransientWindowController::Get()->observers_) {
+        observer.OnDidRestackTransientChildAbove(window_, *it);
+      }
     }
   }
 }