[iOS Clean] Created OverlayService.

ios/clean/chrome/browser/ui/overlays/browser_coordinator+overlay_support.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_WEB_OVERLAY_COORDINATOR_H_
+#define IOS_CLEAN_CHROME_BROWSER_UI_OVERLAYS_WEB_OVERLAY_COORDINATOR_H_
+
+#import <Foundation/Foundation.h>
+
+#import "ios/shared/chrome/browser/ui/coordinators/browser_coordinator.h"
+
+class OverlayQueue;
+
+// Interface exposing functionality to support being displayed via
+// OverlayService.
+@interface BrowserCoordinator (OverlaySupport)
+
+// Whether this BrowserCoordinator supports overlaying.  If NO, it cannot be
+// presented via OverlayService.  If YES, this coordinator is expected to call
+// |-overlayWasStopped| from its |-stop| to allow the next queued overlay to
+// be started.
+// Defaults to NO.
+@property(nonatomic, readonly) BOOL supportsOverlaying;

[kkhorimoto, 2017/06/23 06:11:15]

Not sure if this is the best solution.  Originally, this was handled in
OverlayCoordinator's |-stop|, but that requires having all UI presented as an
overlay to subclass that class.  Moving the functionality to a category allows
more flexibility, but requires trusting users of the service to follow the
guidelines in the comment (i.e. if |supportsOverlaying| returns YES, but
|-overlayWasStopped| is not called, the overlay scheduler will never show the
next overlay).

+
+// The queue used to present this overlay.
+@property(nonatomic, assign) OverlayQueue* queue;
+
+// Starts overlaying this coordinator over |overlayParent|.
+- (void)startOverlayingCoordinator:(BrowserCoordinator*)overlayParent;
+
+// Called when the overay is stopped so that the OverlayService can be notified.

[marq (ping after 24h), 2017/06/21 09:41:53]

Spelling: overlay.

[kkhorimoto, 2017/06/23 06:11:15]

Done.

+- (void)overlayWasStopped;
+
+// Performs cleanup tasks for the overlay.  This allows for deterministic
+// cleanup to occur for coordinators whose UI has not been started. Rather than
+// relying on |-dealloc| to perform cleanup, |-cancelOverlay| can be used to
+// perform cleanup tasks deterministically.
+- (void)cancelOverlay;
+
+@end
+
+#endif  // IOS_CLEAN_CHROME_BROWSER_UI_OVERLAYS_WEB_OVERLAY_COORDINATOR_H_