Introduce ash mojo interface for lock screen action handlers

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index 0a5fb1535017445c8b0bfde0789d97c1c1707e22..b6448b15be1b36de279c627e38844e20c2cdf2b3 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -89,6 +89,7 @@ namespace ash {
 
 class AcceleratorController;
 class AccessibilityDelegate;
+class ActionHandlerStateController;
 class AppListDelegateImpl;
 class AshNativeCursorManager;
 class AshTouchTransformController;
@@ -293,6 +294,9 @@ class ASH_EXPORT Shell : public SessionObserver,
   AccessibilityDelegate* accessibility_delegate() {
     return accessibility_delegate_.get();
   }
+  ActionHandlerStateController* action_handler_state_controller() {
+    return action_handler_state_controller_.get();
+  }
   app_list::AppList* app_list() { return app_list_.get(); }
   const scoped_refptr<base::SequencedWorkerPool>& blocking_pool() {
     return blocking_pool_;
@@ -665,6 +669,8 @@ class ASH_EXPORT Shell : public SessionObserver,
 
   std::unique_ptr<AcceleratorController> accelerator_controller_;
   std::unique_ptr<AccessibilityDelegate> accessibility_delegate_;
+  std::unique_ptr<ActionHandlerStateController>
+      action_handler_state_controller_;
   std::unique_ptr<BrightnessControlDelegate> brightness_control_delegate_;
   std::unique_ptr<CastConfigController> cast_config_;
   std::unique_ptr<DragDropController> drag_drop_controller_;