[ObjC ARC] Converts ios/chrome/browser/ui:ui_internal_arc to ARC.

ios/chrome/browser/ui/preload_controller.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_CHROME_BROWSER_UI_PRELOAD_CONTROLLER_H_
 #define IOS_CHROME_BROWSER_UI_PRELOAD_CONTROLLER_H_
 
 #import <UIKit/UIKit.h>
 
 #include <memory>
@@ skipping 33 matching lines @@
                                         PrefObserverDelegate,
                                         PreloadProvider,
                                         TabDelegate,
                                         CRConnectionTypeObserverBridge>
 // The URL of the currently prerendered Tab.  Empty if there is no prerendered
 // Tab.
 @property(nonatomic, readonly, assign) GURL prerenderedURL;
 // The URL of the currently prefetched content.  Empty if there is no prefetched
 // content.
 @property(nonatomic, readonly, assign) GURL prefetchedURL;
-@property(nonatomic, assign) id<PreloadControllerDelegate> delegate;
+@property(nonatomic, weak) id<PreloadControllerDelegate> delegate;
 
 // Designated initializer.
 - (instancetype)initWithBrowserState:(ios::ChromeBrowserState*)browserState;
 
 // Called when the browser state this object was initialized with is being
 // destroyed.
 - (void)browserStateDestroyed;
 
 // Returns the currently prerendered WebState, or nil if none exists.  After
 // this method is called, the PrerenderController reverts to a non-prerendering
 // state.
 - (std::unique_ptr<web::WebState>)releasePrerenderContents;
 
 // Returns true if the content of |url| has been prefetched.
 - (BOOL)hasPrefetchedURL:(const GURL&)url;
 @end
 
 #endif  // IOS_CHROME_BROWSER_UI_PRELOAD_CONTROLLER_H_