[iOS Clean] Added dialogs UI support.

ios/clean/chrome/browser/ui/dialogs/dialog_button_item.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_ITEM_H_
+#define IOS_CLEAN_CHROME_BROWSER_UI_DIALOGS_DIALOG_BUTTON_ITEM_H_
+
+#import <UIKit/UIKit.h>
+
+// Enum type to describe the style of buttons to use.
+enum class DialogButtonStyle : short { DEFAULT, CANCEL, DESTRUCTIVE };

[marq (ping after 24h), 2017/06/14 10:52:14]

Define the semantics of each value.

Set an explicit value for the first item.

Side note: Should we standardize on 'enum class' in the new architecture?

[kkhorimoto, 2017/06/23 06:24:17]

Done.  I definitely think we should be using enum classes over normal enums. 
The only situation I can think of where I still use normal enums is for array
index constant (e.g. DeprecatedSerializationIndices in
crw_session_certificate_policy_cache_storage.mm).  These are usually
implementation details though, so I think it would be reasonable to use only
enum classes in header files.

+
+// An object encapsulating the data necessary to set up a dialog's text field.

[marq (ping after 24h), 2017/06/14 10:52:14]

Class is for a 'button item', but the comment references a 'text field'. Please
clarify.

[kkhorimoto, 2017/06/23 06:24:17]

Done.

+@interface DialogButtonItem : NSObject
+
+// Factory method for item creation.

[marq (ping after 24h), 2017/06/14 10:52:14]

Document the preconditions you are DCHECKING for in the initailizer

[kkhorimoto, 2017/06/23 06:24:17]

Done.

++ (instancetype)itemWithText:(NSString*)text
+                       style:(DialogButtonStyle)style
+                         tag:(id)tag;
+
+// DialogTextFieldItems 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, strong) NSString* text;
+
+// The placehodler text to display in the text field, if any.
+@property(nonatomic, readonly) DialogButtonStyle style;
+
+// The tag passed to the factory method.  This is used to identify the button
+// tapped for DialogDismissalCommands.
+@property(nonatomic, readonly, strong) id tag;
+
+@end
+#endif  // IOS_CLEAN_CHROME_BROWSER_UI_DIALOGS_DIALOG_BUTTON_ITEM_H_