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

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

Index: ios/chrome/browser/ui/stack_view/stack_card.mm
diff --git a/ios/chrome/browser/ui/stack_view/stack_card.mm b/ios/chrome/browser/ui/stack_view/stack_card.mm
index e809fbbb1693db67a211de703fb4751451867242..a53073660b1e009d18cd3dbdd6eb803a83217ca3 100644
--- a/ios/chrome/browser/ui/stack_view/stack_card.mm
+++ b/ios/chrome/browser/ui/stack_view/stack_card.mm
@@ -5,14 +5,17 @@
 #import "ios/chrome/browser/ui/stack_view/stack_card.h"
 
 #include "base/logging.h"
-#import "base/mac/scoped_nsobject.h"
 #import "ios/chrome/browser/ui/rtl_geometry.h"
 #import "ios/chrome/browser/ui/stack_view/card_view.h"
 #import "ios/chrome/browser/ui/ui_util.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 @interface StackCard () {
-  id<StackCardViewProvider> _viewProvider;
-  base::scoped_nsobject<CardView> _view;
+  __weak id<StackCardViewProvider> _viewProvider;
+  CardView* _view;
 }
 
 // The pixel-aligned frame generated by applying |self.layout| under the current
@@ -47,18 +50,17 @@
 
 - (void)releaseView {
   if (self.viewIsLive)
-    _view.reset();
+    _view = nil;
 }
 
 #pragma mark - Properties
 
 - (CardView*)view {
   if (!_view) {
-    _view.reset([[_viewProvider cardViewWithFrame:self.frame forStackCard:self]
-        retain]);
-    _view.get().isActiveTab = _isActiveTab;
+    _view = [_viewProvider cardViewWithFrame:self.frame forStackCard:self];
+    _view.isActiveTab = _isActiveTab;
   }
-  return _view.get();
+  return _view;
 }
 
 - (void)setLayout:(LayoutRect)layout {
@@ -91,7 +93,7 @@
 
 - (void)setIsActiveTab:(BOOL)isActiveTab {
   _isActiveTab = isActiveTab;
-  _view.get().isActiveTab = _isActiveTab;
+  _view.isActiveTab = _isActiveTab;
 }
 
 - (BOOL)viewIsLive {