Add CRWNativeContent willBeDismissed.

ios/web/public/web_state/ui/crw_native_content.h

 // Copyright 2012 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_WEB_PUBLIC_WEB_STATE_UI_CRW_NATIVE_CONTENT_H_
 #define IOS_WEB_PUBLIC_WEB_STATE_UI_CRW_NATIVE_CONTENT_H_
 
 #import <UIKit/UIKit.h>
 
 #import "ios/web/public/block_types.h"
@@ skipping 67 matching lines @@
 
 // Enables or disables usage of web views inside the native controller.
 - (void)setWebUsageEnabled:(BOOL)webUsageEnabled;
 
 // Enables or disables the scrolling in the native view (when available).
 - (void)setScrollEnabled:(BOOL)enabled;
 
 // Called when a snapshot of the content will be taken.
 - (void)willUpdateSnapshot;
 
+// Notifies the CRWNativeContent that it will be removed from superview.
+- (void)willBeDismissed;
+
 // The URL that will be displayed to the user when presenting this native
 // content.
 - (GURL)virtualURL;
 
 @end
 
 // CRWNativeContent delegate protocol.
 @protocol CRWNativeContentDelegate<NSObject>
 
 @optional
 // Called when the content supplies a new title.
 - (void)nativeContent:(id)content titleDidChange:(NSString*)title;
 
 @end
 
 #endif  // IOS_WEB_PUBLIC_WEB_STATE_UI_CRW_NATIVE_CONTENT_H_