[iOS Clean] Created OverlayService.

ios/clean/chrome/browser/ui/overlays/overlay_queue.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 IOS_CLEAN_CHROME_BROWSER_UI_OVERLAYS_OVERLAY_QUEUE_H_
+#define IOS_CLEAN_CHROME_BROWSER_UI_OVERLAYS_OVERLAY_QUEUE_H_
+
+#import <Foundation/Foundation.h>
+
+#import "ios/clean/chrome/browser/ui/overlays/overlay_coordinator.h"
+#import "ios/web/public/web_state/web_state_user_data.h"
+
+@protocol OverlaySchedulerCommands;
+
+// Class used to enqueue overlay coordinators that are requested by a WebState.
+// It uses OverlaySchedulerCommands to communicate with OverlayScheduler
+// to decide when to display the overlay UI.
+class OverlayQueue : public web::WebStateUserData<OverlayQueue> {
+ public:
+  ~OverlayQueue() override;
+
+  // Factory method that instantaites a OverlayQueue for |web_state| that
+  // uses |dispatcher| to send overlay scheduling commands.
+  static void CreateForWebState(web::WebState* web_state,
+                                id<OverlaySchedulerCommands> dispatcher);
+
+  // Adds |overlay_coordinator| to the queue and schedules its presentation.
+  void AddOverlay(OverlayCoordinator* overlay_coordinator);
+  // Removes the currently displayed overlay and adds |overlay_coordinator| to
+  // the front of the queue to be displayed immediately.
+  void ReplaceVisibleOverlay(OverlayCoordinator* overlay_coordinator);
+  // Returns whether there are any queued overlays.
+  bool HasQueuedOverlays() const;
+  // Displays the next overlay over |web_coordinator|'s UI.  |web_coordinator|
+  // is expected to be displaying the web view that requested the overlay.
+  void StartNextOverlay(BrowserCoordinator* web_coordinator);
+  // Returns whether an overlay is curently started.
+  bool IsShowingOverlay() const;
+  // Notifies the OverlayQueue that |overlay_coordinator| was stopped.
+  void OverlayWasStopped(OverlayCoordinator* overlay_coordinator);
+  // Cancels all queued overlays for this WebState.  If one is being displayed,
+  // it will be stopped and cancelled.
+  void CancelOverlays();
+
+ private:
+  friend class web::WebStateUserData<OverlayQueue>;
+  // The WebState with which this presenter is associated.
+  web::WebState* web_state_;
+  // The OverlayScheduler dispatcher passed on construction.
+  __weak id<OverlaySchedulerCommands> dispatcher_;
+  // The queue of overlays that were added for this WebState.  Overlays will be
+  // removed when they are stopped or when they

[marq (ping after 24h), 2017/06/14 10:02:32]

This comment now has me on tenterhooks ... ;-)

[kkhorimoto, 2017/06/15 08:26:28]

Hah just trying to keep it interesting :)

+  NSMutableArray<OverlayCoordinator*>* overlays_;
+  // Whether the first overlay in |overlays_| is started.

[marq (ping after 24h), 2017/06/14 10:02:32]

If |overlays_| is empty, what value does this have?

[kkhorimoto, 2017/06/15 08:26:28]

It returns false; comments have been updated.

+  bool showing_overlay_;
+
+  // Private constructor.  New instances should be created via
+  // CreateForWebState() and accessed via FromWebState().
+  explicit OverlayQueue(web::WebState* web_state,
+                        id<OverlaySchedulerCommands> dispatcher);
+
+  DISALLOW_COPY_AND_ASSIGN(OverlayQueue);
+};
+#endif  // IOS_CLEAN_CHROME_BROWSER_UI_OVERLAYS_OVERLAY_QUEUE_H_