Introduce ash mojo interface for lock screen action handlers

ash/action_handler/action_handler_state_controller.h

Index: ash/action_handler/action_handler_state_controller.h
diff --git a/ash/action_handler/action_handler_state_controller.h b/ash/action_handler/action_handler_state_controller.h
new file mode 100644
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+++ b/ash/action_handler/action_handler_state_controller.h
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+// 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_ACTION_HANDLER_ACTION_HANDLER_STATE_CONTROLLER_H_
+#define ASH_ACTION_HANDLER_ACTION_HANDLER_STATE_CONTROLLER_H_
+
+#include "ash/action_handler/action_handler_state_observer.h"
+#include "ash/public/interfaces/action_handler.mojom.h"
+#include "base/macros.h"
+#include "base/observer_list.h"
+#include "mojo/public/cpp/bindings/binding_set.h"
+
+namespace ash {
+
+// Controller that ash can use to request a predefined set of actions to be
+// performed by clients.
+// The controller provides an interface to:
+//  * Send a request to the client to handle an action.
+//  * Observe the state of support for an action as reported by the current ash
+//    client.
+// Currently, only single action is supported - creating new note on the lock
+// screen.
+class ActionHandlerStateController
+    : public mojom::ActionHandlerStateController {
+ public:
+  ActionHandlerStateController();
+  ~ActionHandlerStateController() override;
+
+  void AddObserver(ActionHandlerStateObserver* observer);
+  void RemoveObserver(ActionHandlerStateObserver* observer);
+
+  void BindRequest(mojom::ActionHandlerStateControllerRequest request);
+
+  // Gets last known handler state for the action.
+  // It will return kNotSupported if an action handler has not been set using
+  // |SetActionHandler|.
+  mojom::ActionHandlerState GetState(mojom::ActionHandlerAction action);
+
+  // If an action handler is set, send it a request to handle the action.
+  void RequestHandleAction(mojom::ActionHandlerAction action);
+
+  // mojom::ActionHandlerStateController impl:
+  void SetActionHandler(mojom::ActionHandlerPtr action_handler) override;
+  void UpdateActionState(mojom::ActionHandlerAction action,
+                         mojom::ActionHandlerState state) override;
+
+ private:
+  // Notifies the observers that state for the action has been updated.
+  void NotifyActionStateChanged(mojom::ActionHandlerAction action);
+
+  // Last known state for new_note action.
+  mojom::ActionHandlerState new_note_state_ =
+      mojom::ActionHandlerState::kNotSupported;
+
+  base::ObserverList<ActionHandlerStateObserver> observers_;
+
+  mojo::BindingSet<mojom::ActionHandlerStateController> bindings_;
+
+  mojom::ActionHandlerPtr action_handler_;
+
+  DISALLOW_COPY_AND_ASSIGN(ActionHandlerStateController);
+};
+
+}  // namespace ash
+
+#endif  // ASH_ACTION_HANDLER_ACTION_HANDLER_STATE_CONTROLLER_H_