Adds sizing, maximizing, minimizing to simple_wm

mash/simple_wm/simple_wm.h

Index: mash/simple_wm/simple_wm.h
diff --git a/mash/simple_wm/simple_wm.h b/mash/simple_wm/simple_wm.h
index d0dc5a004144f0c91381f9a5f3d30b7a1d4ce61a..e6be287cc06f04971b04560cf5e5a0cf55e3eabf 100644
--- a/mash/simple_wm/simple_wm.h
+++ b/mash/simple_wm/simple_wm.h
@@ -52,6 +52,7 @@ class SimpleWM : public service_manager::Service,
   class WindowListModel;
   class WindowListModelObserver;
   class WindowListView;
+  class WorkspaceLayoutManager;
 
   // service_manager::Service:
   void OnStart() override;
@@ -113,6 +114,7 @@ class SimpleWM : public service_manager::Service,
   std::unique_ptr<aura::MusContextFactory> compositor_context_factory_;
   std::map<aura::Window*, FrameView*> client_window_to_frame_view_;
   std::unique_ptr<WindowListModel> window_list_model_;
+  std::unique_ptr<WorkspaceLayoutManager> workspace_layout_manager_;
 
   bool started_ = false;