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

ios/chrome/browser/ui/bookmarks/bookmark_collection_view_background.mm

 // 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.
 
 #include "ios/chrome/browser/ui/bookmarks/bookmark_collection_view_background.h"
 
-#include "base/mac/objc_property_releaser.h"
 #import "ios/third_party/material_roboto_font_loader_ios/src/src/MaterialRobotoFontLoader.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 NSString* const kBookmarkGrayStar = @"bookmark_gray_star_large";
 const CGFloat kEmptyBookmarkTextSize = 16.0;
 // Offset of the image view on top of the text.
 const CGFloat kImageViewOffsetFromText = 5.0;
 }  // namespace
 
-@interface BookmarkCollectionViewBackground () {
-  base::mac::ObjCPropertyReleaser
-      _propertyReleaser_BookmarkBookmarkCollectionViewBackground;
-}
+@interface BookmarkCollectionViewBackground ()
 
 // Star image view shown on top of the label.
 @property(nonatomic, retain) UIImageView* emptyBookmarksImageView;
 // Label centered on the view showing the empty bookmarks text.
 @property(nonatomic, retain) UILabel* emptyBookmarksLabel;
 
 @end
 
 @implementation BookmarkCollectionViewBackground
 
 @synthesize emptyBookmarksImageView = _emptyBookmarksImageView;
 @synthesize emptyBookmarksLabel = _emptyBookmarksLabel;
 
 - (instancetype)initWithFrame:(CGRect)frame {
   self = [super initWithFrame:frame];
   if (self) {
-    _propertyReleaser_BookmarkBookmarkCollectionViewBackground.Init(
-        self, [BookmarkCollectionViewBackground class]);
     _emptyBookmarksImageView = [self newBookmarkImageView];
     [self addSubview:_emptyBookmarksImageView];
     _emptyBookmarksLabel = [self newEmptyBookmarkLabel];
     [self addSubview:_emptyBookmarksLabel];
   }
   return self;
 }
 
 - (void)layoutSubviews {
   [super layoutSubviews];
@@ skipping 42 matching lines @@
 - (CGRect)bookmarkImageViewFrame {
   const CGRect labelRect = [self emptyBookmarkLabelFrame];
   const CGSize imageViewSize = self.emptyBookmarksImageView.image.size;
   return CGRectMake((CGRectGetWidth(self.bounds) - imageViewSize.width) / 2.0,
                     CGRectGetMinY(labelRect) - kImageViewOffsetFromText -
                         imageViewSize.height,
                     imageViewSize.width, imageViewSize.height);
 }
 
 @end