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

ios/chrome/browser/ui/collection_view/collection_view_controller.h

 // Copyright 2016 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_COLLECTION_VIEW_COLLECTION_VIEW_CONTROLLER_H_
 #define IOS_CHROME_BROWSER_UI_COLLECTION_VIEW_COLLECTION_VIEW_CONTROLLER_H_
 
 #import "ios/chrome/browser/ui/collection_view/collection_view_model.h"
 #import "ios/chrome/browser/ui/material_components/app_bar_presenting.h"
 #import "ios/third_party/material_components_ios/src/components/Collections/src/MaterialCollections.h"
 
 @class CollectionViewItem;
 
 typedef NS_ENUM(NSInteger, CollectionViewControllerStyle) {
   // A simple collection view controller.
   CollectionViewControllerStyleDefault,
   // A collection view controller with an app bar.
   CollectionViewControllerStyleAppBar,
 };
 
 // Chrome-specific Material Design collection view controller. With
 // CollectionViewControllerStyleAppBar, it features an app bar in the card
 // style.
 @interface CollectionViewController
     : MDCCollectionViewController<AppBarPresenting>
 
 // The model of this controller.
-@property(nonatomic, readonly)
+@property(strong, nonatomic, readonly)
     CollectionViewModel<CollectionViewItem*>* collectionViewModel;
 
 // Initializer with the desired style.
 - (instancetype)initWithStyle:(CollectionViewControllerStyle)style
     NS_DESIGNATED_INITIALIZER;
 - (instancetype)initWithCollectionViewLayout:(UICollectionViewLayout*)layout
     NS_UNAVAILABLE;
 - (instancetype)initWithNibName:(NSString*)nibNameOrNil
                          bundle:(NSBundle*)nibBundleOrNil NS_UNAVAILABLE;
 - (instancetype)initWithCoder:(NSCoder*)aDecoder NS_UNAVAILABLE;
@@ skipping 50 matching lines @@
 // state. Must be called by subclasses if they override this method in order to
 // maintain this functionality.
 - (void)scrollViewWillEndDragging:(UIScrollView*)scrollView
                      withVelocity:(CGPoint)velocity
               targetContentOffset:(inout CGPoint*)targetContentOffset
     NS_REQUIRES_SUPER;
 
 @end
 
 #endif  // IOS_CHROME_BROWSER_UI_COLLECTION_VIEW_COLLECTION_VIEW_CONTROLLER_H_