[iOS Clean] Created OverlayService.

ios/clean/chrome/browser/ui/overlay_service/internal/overlay_service_impl.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_INTERNAL_OVERLAY_SERVICE_IMPL_H_
+#define IOS_CLEAN_CHROME_BROWSER_UI_OVERLAYS_INTERNAL_OVERLAY_SERVICE_IMPL_H_
+
+#import "ios/clean/chrome/browser/ui/overlay_service/overlay_service.h"
+#import "ios/shared/chrome/browser/ui/browser_list/browser_list_observer.h"
+
+class BrowserList;
+
+// Concrete subclass of OverlayService.
+class OverlayServiceImpl : public BrowserListObserver, public OverlayService {
+ public:
+  // Constructor for an OverlayService that schedules overlays for the Browsers
+  // in |browser_list|.
+  OverlayServiceImpl(BrowserList* browser_list);
+  ~OverlayServiceImpl() override = default;
+
+ private:
+  // The BrowserList passed on implementation.
+  BrowserList* browser_list_;
+
+  // BrowserListObserver:
+  void OnBrowserCreated(BrowserList* browser_list, Browser* browser) override;
+  void OnBrowserRemoved(BrowserList* browser_list, Browser* browser) override;
+
+  // KeyedService:
+  void Shutdown() override;
+
+  // OverlayService:
+  bool IsBrowserShowingOverlay(Browser* browser) const override;
+  void ReplaceVisibleOverlay(BrowserCoordinator* overlay_coordinator,
+                             Browser* browser) override;
+  void ShowOverlayForWebState(BrowserCoordinator* overlay_coordinator,
+                              web::WebState* web_state) override;
+  void SetWebStateParentCoordinator(BrowserCoordinator* parent_coordinator,
+                                    web::WebState* web_state) override;
+  void ShowOverlayForBrowser(BrowserCoordinator* overlay_coordinator,
+                             BrowserCoordinator* parent_coordiantor,
+                             Browser* browser) override;
+  void CancelOverlays() override;
+  void CancelOverlayForWebState(web::WebState* web_state) override;
+
+  // Starts or stops an OverlayScheduler for |browser|.
+  void StartSchedulerForBrowser(Browser* browser);
+  void StopSchedulerForBrowser(Browser* browser);
+
+  DISALLOW_COPY_AND_ASSIGN(OverlayServiceImpl);
+};
+
+#endif  // IOS_CLEAN_CHROME_BROWSER_UI_OVERLAYS_INTERNAL_OVERLAY_SERVICE_IMPL_H_