[iOS Clean] Added dialogs UI support.

ios/clean/chrome/browser/ui/dialogs/dialog_coordinator+subclassing.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_DIALOGS_DIALOG_COORDINATOR_SUBCLASSING_H_
+#define IOS_CLEAN_CHROME_BROWSER_UI_DIALOGS_DIALOG_COORDINATOR_SUBCLASSING_H_
+
+#import <UIKit/UIKit.h>
+
+#import "ios/clean/chrome/browser/ui/dialogs/dialog_coordinator.h"
+
+@class DialogMediator;
+
+// Interface used to expose DialogCoordinator configuration to subclasses.
+@interface DialogCoordinator (Subclassing)
+
+// The type of dialog UI that should be started for this coordinator.  Defaults
+// to UIAlertControllerStyleAlert.
+@property(nonatomic, readonly) UIAlertControllerStyle alertStyle;
+
+// The mediator that will be used to configure the DialogConsumer.  The value is
+// expected to return non-nil before DialogCoordinator's |-start| is called.
+@property(nonatomic, readonly) DialogMediator* mediator;
+
+@end
+
+#endif  // IOS_CLEAN_CHROME_BROWSER_UI_DIALOGS_DIALOG_COORDINATOR_SUBCLASSING_H_