[iOS] Add experimental new keyboard accessory view.

ios/chrome/browser/ui/toolbar/keyboard_accessory_view_protocol.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_PROTOCOL_H_
+#define IOS_CHROME_BROWSER_UI_TOOLBAR_KEYBOARD_ACCESSORY_VIEW_PROTOCOL_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 touch up occured in the the Camera Search
+// button.
+- (void)keyboardAccessoryCameraSearchTouchUpInside;
+
+// 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
+};
+
+// Protocol the keyboard accessory views must implement.
+@protocol KeyboardAccessoryViewProtocol
+
+// The mode in which the KeyboardAccessoryView is in.
+@property(nonatomic) KeyboardAccessoryViewMode mode;
+
+@end
+
+#endif  // IOS_CHROME_BROWSER_UI_TOOLBAR_KEYBOARD_ACCESSORY_VIEW_PROTOCOL_H_