Revert of [ObjC ARC] Converts ios/chrome/browser/ui/stack_view:stack_view to ARC.

ios/chrome/browser/ui/stack_view/stack_view_toolbar_controller.mm

 // 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.
 
 #import "ios/chrome/browser/ui/stack_view/stack_view_toolbar_controller.h"
 
 #include "base/mac/foundation_util.h"
 #include "base/metrics/user_metrics.h"
 #include "base/metrics/user_metrics_action.h"
 #import "ios/chrome/browser/ui/image_util.h"
 #import "ios/chrome/browser/ui/rtl_geometry.h"
 #include "ios/chrome/browser/ui/toolbar/new_tab_button.h"
 #import "ios/chrome/browser/ui/uikit_ui_util.h"
 
-#if !defined(__has_feature) || !__has_feature(objc_arc)
-#error "This file requires ARC support."
-#endif
-
 using base::UserMetricsAction;
 
 namespace {
 const CGFloat kNewTabLeadingOffset = 10.0;
 const int kBackgroundViewColor = 0x282C32;
 const CGFloat kBackgroundViewColorAlpha = 0.95;
 }
 
 @implementation StackViewToolbarController {
-  UIView* _stackViewToolbar;
-  NewTabButton* _openNewTabButton;
+  base::scoped_nsobject<UIView> _stackViewToolbar;
+  base::scoped_nsobject<NewTabButton> _openNewTabButton;
 }
 
 - (instancetype)initWithStackViewToolbar {
   self = [super initWithStyle:ToolbarControllerStyleDarkMode];
   if (self) {
-    _stackViewToolbar =
-        [[UIView alloc] initWithFrame:[self specificControlsArea]];
+    _stackViewToolbar.reset(
+        [[UIView alloc] initWithFrame:[self specificControlsArea]]);
     [_stackViewToolbar setAutoresizingMask:UIViewAutoresizingFlexibleHeight |
                                            UIViewAutoresizingFlexibleWidth];
 
-    _openNewTabButton = [[NewTabButton alloc] initWithFrame:CGRectZero];
+    _openNewTabButton.reset([[NewTabButton alloc] initWithFrame:CGRectZero]);
 
     [_openNewTabButton
         setAutoresizingMask:UIViewAutoresizingFlexibleTopMargin |
                             UIViewAutoresizingFlexibleTrailingMargin()];
     CGFloat buttonSize = [_stackViewToolbar bounds].size.height;
     // Set the button's position.
     LayoutRect newTabButtonLayout = LayoutRectMake(
         kNewTabLeadingOffset, [_stackViewToolbar bounds].size.width, 0,
         buttonSize, buttonSize);
     [_openNewTabButton setFrame:LayoutRectGetRect(newTabButtonLayout)];
     // Set additional button action.
     [_openNewTabButton addTarget:self
                           action:@selector(recordUserMetrics:)
                 forControlEvents:UIControlEventTouchUpInside];
 
     self.shadowView.alpha = 0.0;
     self.backgroundView.image = nil;
     self.backgroundView.backgroundColor =
         UIColorFromRGB(kBackgroundViewColor, kBackgroundViewColorAlpha);
 
     [_stackViewToolbar addSubview:_openNewTabButton];
     [self.view addSubview:_stackViewToolbar];
   }
   return self;
 }
 
 - (NewTabButton*)openNewTabButton {
-  return _openNewTabButton;
+  return _openNewTabButton.get();
 }
 
 - (IBAction)recordUserMetrics:(id)sender {
-  if (sender == _openNewTabButton)
+  if (sender == _openNewTabButton.get())
     base::RecordAction(UserMetricsAction("MobileToolbarStackViewNewTab"));
   else
     [super recordUserMetrics:sender];
 }
 
 @end