Introduce window container to be used by lock screen app windows

ash/wm/lock_action_handler_layout_manager.h

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ASH_WM_LOCK_ACTION_HANDLER_LAYOUT_MANAGER_H_
+#define ASH_WM_LOCK_ACTION_HANDLER_LAYOUT_MANAGER_H_
+
+#include "ash/ash_export.h"
+#include "ash/public/cpp/shelf_types.h"
+#include "ash/shelf/wm_shelf_observer.h"
+#include "ash/tray_action/tray_action_observer.h"
+#include "ash/wm/lock_layout_manager.h"
+#include "base/macros.h"
+#include "base/scoped_observer.h"
+
+namespace ash {
+
+class TrayAction;
+class WmShelf;
+
+// Window layout manager for windows intended to handle lock tray actions.
+// Since "new note" is currently the only supported action, the layout
+// manager uses new note tray action state to determine it state.
+// The layout is intended to be used for two window containers:
+// * LockActionHandlerContainer - parents handler windows when the new note
+//   action is in active state, i.e. handler windows should be visible on
+//   top of lock screen.
+// * LockActionHandlerContainer_Background - parents handler windows when the
+//   new note action is in background state, i.e. handler windows should be
+//   visible below the lock screen UI.
+// The layout manager will observe new note action state changes and reparent
+// the associated container's children as needed.
+// The windows in this container will have be maximized, if possible. If they
+// are not resible, they will be centered on the screen - similar to windows
+// in lock screen container.
+// Unlike lock layout manager, when maximizing windows, this layout manager will
+// ensure that the windows do not obscure the system shelf.
+class ASH_EXPORT LockActionHandlerLayoutManager : public LockLayoutManager,
+                                                  public WmShelfObserver,
+                                                  public TrayActionObserver {
+ public:
+  LockActionHandlerLayoutManager(aura::Window* window, WmShelf* wm_shelf);
+  ~LockActionHandlerLayoutManager() override;
+
+  // WmSnapToPixelLayoutManager:
+  void OnWindowAddedToLayout(aura::Window* child) override;
+  void OnChildWindowVisibilityChanged(aura::Window* child,
+                                      bool visibile) override;
+
+  // WmShelfObserver:
+  void WillChangeVisibilityState(ShelfVisibilityState visibility) override;
+
+  // TrayActionObserver:
+  void OnLockScreenNoteStateChanged(mojom::TrayActionState state) override;
+
+ private:
+  aura::Window* GetActiveActionHandlerContainer(mojom::TrayActionState state);
+
+  ScopedObserver<WmShelf, WmShelfObserver> shelf_observer_;
+  ScopedObserver<TrayAction, TrayActionObserver> tray_action_observer_;
+
+  DISALLOW_COPY_AND_ASSIGN(LockActionHandlerLayoutManager);
+};
+
+}  // namespace ash
+
+#endif  // ASH_WM_LOCK_ACTION_HANDLER_LAYOUT_MANAGER_H_