Converts DockedWindowLayoutManager to common ash/wm types

ash/wm/aura/aura_layout_manager_adapter.h

Index: ash/wm/aura/aura_layout_manager_adapter.h
diff --git a/ash/wm/aura/aura_layout_manager_adapter.h b/ash/wm/aura/aura_layout_manager_adapter.h
index 88a05140566e1d321ecfb7752e3b6c5cdc5034e2..e5e7ac45a1333dab7a5c4c2d54e39e7ac9d6655f 100644
--- a/ash/wm/aura/aura_layout_manager_adapter.h
+++ b/ash/wm/aura/aura_layout_manager_adapter.h
@@ -25,6 +25,8 @@ class ASH_EXPORT AuraLayoutManagerAdapter : public aura::LayoutManager {
       std::unique_ptr<WmLayoutManager> wm_layout_manager);
   ~AuraLayoutManagerAdapter() override;
 
+  WmLayoutManager* wm_layout_manager() { return wm_layout_manager_.get(); }
+
   // aura::LayoutManager:
   void OnWindowResized() override;
   void OnWindowAddedToLayout(aura::Window* child) override;