Implement automatic layout and stacking for docked windows

ash/wm/panels/panel_layout_manager.h

Index: ash/wm/panels/panel_layout_manager.h
diff --git a/ash/wm/panels/panel_layout_manager.h b/ash/wm/panels/panel_layout_manager.h
index 9d72fc1af535a8668ac34a1e95739d1900df75d2..f3b128cb18e74abf875778b553c9b0fd50506e48 100644
--- a/ash/wm/panels/panel_layout_manager.h
+++ b/ash/wm/panels/panel_layout_manager.h
@@ -172,8 +172,8 @@ class ASH_EXPORT PanelLayoutManager
   // Tracks the visibility of the shelf. Defaults to false when there is no
   // shelf.
   bool shelf_hidden_;
-  // The last active panel. Used to maintain stacking even if no panels are
-  // currently focused.
+  // The last active panel. Used to maintain stacking order even if no panels
+  // are currently focused.
   aura::Window* last_active_panel_;
   base::WeakPtrFactory<PanelLayoutManager> weak_factory_;