[iOS] Factor out the KeyboardAccessoryView.

ios/chrome/browser/ui/toolbar/keyboard_accessory_view.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_CHROME_BROWSER_UI_TOOLBAR_KEYBOARD_ACCESSORY_VIEW_H_
+#define IOS_CHROME_BROWSER_UI_TOOLBAR_KEYBOARD_ACCESSORY_VIEW_H_
+
+#import <UIKit/UIKIt.h>
+
+// Delegate protocol for the KeyboardAccessoryView.
+@protocol KeyboardAccessoryViewDelegate
+
+// Notifies the delegate that the Voice Search button was pressed.
+- (void)keyboardAccessoryVoiceSearchTouchDown;
+
+// Notifies the delegate that a touch up occured in the the Voice Search button.
+- (void)keyboardAccessoryVoiceSearchTouchUpInside;
+
+// Notifies the delegate that a key with the title |title| was pressed.
+- (void)keyPressed:(NSString*)title;
+
+@end
+
+typedef NS_ENUM(NSInteger, KeyboardAccessoryViewMode) {
+  VOICE_SEARCH = 0,
+  KEY_SHORTCUTS
+};
+
+// Accessory View above the keyboard.
+// Supports two modes: one where a Voice Search button is shown, and one where
+// a list of buttons based on |buttonTitles| is shown.
+// The default mode is the Voice Search mode.
+@interface KeyboardAccessoryView : UIInputView<UIInputViewAudioFeedback>
+
+- (instancetype)initWithCoder:(NSCoder*)aDecoder NS_UNAVAILABLE;
+
+- (instancetype)initWithFrame:(CGRect)frame
+               inputViewStyle:(UIInputViewStyle)inputViewStyle NS_UNAVAILABLE;
+

[marq (ping after 24h), 2017/06/02 09:15:10]

Comment for the initializer, documenting behavior if |buttonTitles| is nil or
empty, etc.

+- (instancetype)initWithButtons:(NSArray<NSString*>*)buttonTitles

[marq (ping after 24h), 2017/06/02 09:15:10]

Optional style nit: Put the designated initializer first, then follow with the
unavailable ones.

[jif, 2017/06/02 13:06:18]

Done.

+                       delegate:(id<KeyboardAccessoryViewDelegate>)delegate
+    NS_DESIGNATED_INITIALIZER;
+
+// The mode in which the KeyboardAccessoryView is in.
+@property(nonatomic) KeyboardAccessoryViewMode mode;
+
+@end
+
+#endif  // IOS_CHROME_BROWSER_UI_TOOLBAR_KEYBOARD_ACCESSORY_VIEW_H_