[ObjC ARC] Converts ios/chrome/today_extension:today_extension to ARC.

ios/chrome/today_extension/notification_center_url_button.mm

 // 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.
 
 #import "ios/chrome/today_extension/notification_center_url_button.h"
 
 #import "base/mac/foundation_util.h"
 #import "base/mac/scoped_block.h"
 #import "base/mac/scoped_nsobject.h"
 #include "base/strings/sys_string_conversions.h"
 #import "ios/chrome/common/physical_web/physical_web_device.h"
 #import "ios/chrome/today_extension/ui_util.h"
 #include "net/base/escape.h"
 #include "ui/base/l10n/l10n_util.h"
 
 namespace {
 const CGFloat kSubtitleFontSize = 14;
 }
 
 @implementation NotificationCenterURLButton {
-  base::mac::ScopedBlock<URLActionBlock> _openURLBlock;
+  URLActionBlock _openURLBlock;
   base::scoped_nsobject<NSString> _url;
   base::scoped_nsobject<UILabel> _subtitleLabel;
   base::scoped_nsobject<UIView> _bottomSeparator;
 }
 
 - (void)openURL:(id)sender {
-  _openURLBlock.get()(_url);
+  if (_openURLBlock) {
+    _openURLBlock(_url);
+  }
 }
 
 - (NSString*)unescapeURLString:(NSString*)urlString {
   std::string escapedURL = base::SysNSStringToUTF8(urlString);
   std::string unescapedURL =
       net::UnescapeURLComponent(escapedURL, net::UnescapeRule::SPACES);
   NSString* unescapedURLString = base::SysUTF8ToNSString(unescapedURL);
   return unescapedURLString;
 }
 
 // Create a button with contextual URL layout.
 - (instancetype)initWithTitle:(NSString*)title
                           url:(NSString*)url
                          icon:(NSString*)icon
                     leftInset:(CGFloat)leftInset
                         block:(URLActionBlock)block {
   self = [super initWithTitle:title
                          icon:nil
                        target:nil
                        action:@selector(openURL:)
               backgroundColor:[UIColor clearColor]
                      inkColor:ui_util::InkColor()
                    titleColor:ui_util::TitleColor()];
   if (self) {
-    _openURLBlock.reset(block, base::scoped_policy::RETAIN);
+    _openURLBlock = [block copy];
     [self setContentVerticalAlignment:UIControlContentVerticalAlignmentTop];
 
     _url.reset([url copy]);
 
     UIImage* iconImage = [[UIImage imageNamed:icon]
         imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate];
     [self setImage:iconImage forState:UIControlStateNormal];
     [[self imageView] setTintColor:ui_util::NormalTintColor()];
 
     CGFloat chromeIconXOffset = leftInset + ui_util::ChromeIconOffset();
@@ skipping 106 matching lines @@
     [_subtitleLabel setTextColor:ui_util::TextColor()];
     [[self imageView] setTintColor:ui_util::NormalTintColor()];
   }
 }
 
 - (void)setSeparatorVisible:(BOOL)visible {
   [_bottomSeparator setHidden:!visible];
 }
 
 @end