Check that child window was not destroyed inside UpdateTransientChildVisibility.

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 2ca145d2420dbdd9f9a2fc81fd785e8e64d7a495..b2840dc46d7a796e9e51bec608ab8edc4f765589 100644
--- a/ui/wm/core/transient_window_manager.cc
+++ b/ui/wm/core/transient_window_manager.cc
@@ -162,8 +162,13 @@ void TransientWindowManager::OnWindowVisibilityChanged(Window* window,
 
   // If the window has transient children, updates the transient children's
   // visiblity as well.
-  for (Window* child : transient_children_)
-    Get(child)->UpdateTransientChildVisibility(visible);
+  Windows transient_children = transient_children_;
+  for (Window* child : transient_children) {
+    // Child window can be removed inside UpdateTransientChildVisibility call.
+    if (std::find(transient_children_.begin(), transient_children_.end(),
+                  child) != transient_children_.end())

[oshima, 2015/11/19 18:05:40]

you need {} in this case

+      Get(child)->UpdateTransientChildVisibility(visible);
+  }
 
   // Remember the show request in |show_on_parent_visible_| and hide it again
   // if the following conditions are met