Fixes bug in handling restacking because of transients

ui/aura/client/transient_window_client_observer.h

Index: ui/aura/client/transient_window_client_observer.h
diff --git a/ui/aura/client/transient_window_client_observer.h b/ui/aura/client/transient_window_client_observer.h
index 27dc39bf44a404750ccdee1666beb2513863b837..7213d827d0d29d4093173b5c3b840ef8da0455a8 100644
--- a/ui/aura/client/transient_window_client_observer.h
+++ b/ui/aura/client/transient_window_client_observer.h
@@ -25,6 +25,16 @@ class AURA_EXPORT TransientWindowClientObserver {
   virtual void OnTransientChildWindowRemoved(Window* parent,
                                              Window* transient_child) = 0;
 
+  // Called when adding or removing a transient results in restacking.
+  // |transient_child| is the window being stacked above |parent|. |parent| is
+  // the window the transient was added or removed from. This is followed by a
+  // call to Window::StackChildAbove() and then
+  // OnDidRestackTransientChildAbove().
+  virtual void OnWillRestackTransientChildAbove(Window* parent,

[msw, 2016/11/21 22:34:49]

optional nit: rename 'stack'->'order' throughout.

[sky, 2016/11/21 22:41:10]

I left this as stack. It better fits with the StackChild* calls in Window as
well as the delegate.

+                                                Window* transient_child) = 0;
+  virtual void OnDidRestackTransientChildAbove(Window* parent,
+                                               Window* transient_child) = 0;
+
  protected:
   virtual ~TransientWindowClientObserver() {}
 };