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

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

 // Copyright 2015 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.
 
 #import "ios/chrome/browser/ui/bookmarks/bookmark_elevated_toolbar.h"
 
-#include "base/mac/objc_property_releaser.h"
 #import "ios/third_party/material_components_ios/src/components/ShadowElevations/src/MaterialShadowElevations.h"
 #import "ios/third_party/material_components_ios/src/components/ShadowLayer/src/MaterialShadowLayer.h"
 
-@implementation BookmarksElevatedToolbar {
-  base::mac::ObjCPropertyReleaser _propertyReleaser_BookmarksElevatedToolbar;
-}
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
 
+@implementation BookmarksElevatedToolbar
 @synthesize shadowLayer = _shadowLayer;
 
-#pragma mark - Lifecycle
-
-- (instancetype)init {
-  self = [super init];
-  if (self) {
-    _propertyReleaser_BookmarksElevatedToolbar.Init(
-        self, [BookmarksElevatedToolbar class]);
-  }
-  return self;
-}
-
 #pragma mark - Properties
 
 - (MDCShadowLayer*)shadowLayer {
   if (!_shadowLayer) {
     _shadowLayer = [[MDCShadowLayer alloc] init];
     _shadowLayer.elevation = MDCShadowElevationNone;
     [self.layer addSublayer:self.shadowLayer];
   }
   return _shadowLayer;
 }
 
 - (void)setShadowElevation:(CGFloat)shadowElevation {
   self.shadowLayer.elevation = shadowElevation;
 }
 
 - (CGFloat)shadowElevation {
   return self.shadowLayer.elevation;
 }
 
 #pragma mark - UIView
 
 - (void)layoutSubviews {
   [super layoutSubviews];
   self.shadowLayer.frame = self.layer.bounds;
 }
 
 @end