[ObjC ARC] Converts ios/web:web to ARC.

ios/web/web_state/ui/crw_wk_script_message_router.h

 // Copyright 2014 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_WEB_STATE_UI_CRW_WK_SCRIPT_MESSAGE_ROUTER_H_
 #define IOS_WEB_WEB_STATE_UI_CRW_WK_SCRIPT_MESSAGE_ROUTER_H_
 
 #import <WebKit/WebKit.h>
 
 // WKUserContentController wrapper that allows adding multiple message handlers
 // for the same message name. CRWWKScriptMessageRouter will route the messages
 // from the underlying user content controller to a designated receiver by
 // matching the message's name and webView.
 @interface CRWWKScriptMessageRouter : NSObject
 
 // Underlying WKUserContentController.
-@property(nonatomic, readonly) WKUserContentController* userContentController;
+@property(nonatomic, weak, readonly)
+    WKUserContentController* userContentController;
 
 // Designated initializer. |userContentController| must not be nil.
 - (instancetype)initWithUserContentController:
     (WKUserContentController*)userContentController NS_DESIGNATED_INITIALIZER;
 
 - (instancetype)init NS_UNAVAILABLE;
 
 // Sets a script message handler. Multiple message handlers can be added for
 // the same message name and long as |webView| are different. Setting |handler|
 // for the same |name| and |webView| pair is an error. |handler| will be called
 // if WKScriptMessage sent by WKUserContentController will match both the |name|
 // and the |webView|.
 - (void)setScriptMessageHandler:(void (^)(WKScriptMessage*))handler
                            name:(NSString*)messageName
                         webView:(WKWebView*)webView;
 
 // Removes a specific message handler.
 - (void)removeScriptMessageHandlerForName:(NSString*)messageName
                                   webView:(WKWebView*)webView;
 
 // Removes all message handlers for the given |webView|.
 - (void)removeAllScriptMessageHandlersForWebView:(WKWebView*)webView;
 
 @end
 
 #endif  // IOS_WEB_WEB_STATE_UI_CRW_WK_SCRIPT_MESSAGE_ROUTER_H_