[iOS Clean] Added dialogs UI support.

ios/clean/chrome/browser/ui/dialogs/dialog_button_configuration.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_BUTTON_CONFIGURATION_H_
+#define IOS_CLEAN_CHROME_BROWSER_UI_DIALOGS_DIALOG_BUTTON_CONFIGURATION_H_
+
+#import <UIKit/UIKit.h>
+
+// Enum type to describe the style of buttons to use.
+enum class DialogButtonStyle : short {
+  DEFAULT = 0,  // Uses default button styling.
+
+  CANCEL,  // Uses styling to indicates that the button cancels the
+           // current action, and leaves things unchanged.
+
+  DESTRUCTIVE  // Uses styling that indicates that the button might change or
+               // delete data.
+};
+
+// An object encapsulating the data necessary to set up a dialog button.
+@interface DialogButtonConfiguration : NSObject
+
+// Factory method for item creation.  |text| must be non-empty, and |identifier|
+// must be non-nil.
++ (instancetype)itemWithText:(NSString*)text
+                       style:(DialogButtonStyle)style
+                  identifier:(id)identifier;
+
+// DialogTextFieldConfigurations should be created through the factory method.
+- (instancetype)init NS_UNAVAILABLE;
+
+// The default text to display in the text field, if any.
+@property(nonatomic, readonly, copy) NSString* text;
+
+// The placehodler text to display in the text field, if any.
+@property(nonatomic, readonly) DialogButtonStyle style;
+
+// The ID passed to the factory method.  This is used to identify the button
+// tapped for DialogDismissalCommands.
+@property(nonatomic, readonly, strong) id identifier;
+
+@end
+#endif  // IOS_CLEAN_CHROME_BROWSER_UI_DIALOGS_DIALOG_BUTTON_CONFIGURATION_H_