Activate windows in topmost containers when a window is hidden.

ash/wm/activation_controller.h

Index: ash/wm/activation_controller.h
diff --git a/ash/wm/activation_controller.h b/ash/wm/activation_controller.h
index 6292add16d28d61b4313fbbc01bdf5567d593c78..a3294ff5cb836cec4c69a8d00497afb928f3c485 100644
--- a/ash/wm/activation_controller.h
+++ b/ash/wm/activation_controller.h
@@ -60,6 +60,12 @@ class ASH_EXPORT ActivationController
   // Returns the next window that should be activated, ignoring |ignore|.
   aura::Window* GetTopmostWindowToActivate(aura::Window* ignore) const;
 
+  // Returns the next window that should be activated in |container| ignoring
+  // the window |ignore|.
+  aura::Window* GetTopmostWindowToActivateInContainer(
+      aura::Window* container,
+      aura::Window* ignore) const;
+
   // True inside ActivateWindow(). Used to prevent recursion of focus
   // change notifications causing activation.
   bool updating_activation_;