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

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

Index: ios/chrome/browser/ui/stack_view/page_animation_util.mm
diff --git a/ios/chrome/browser/ui/stack_view/page_animation_util.mm b/ios/chrome/browser/ui/stack_view/page_animation_util.mm
index a43792e0921d03856b0bc31a432e6dcb40226ed2..3e66bd4c4b76ecaffb79eb2d6e049eef8334fe7d 100644
--- a/ios/chrome/browser/ui/stack_view/page_animation_util.mm
+++ b/ios/chrome/browser/ui/stack_view/page_animation_util.mm
@@ -7,14 +7,11 @@
 #import <QuartzCore/QuartzCore.h>
 #import <UIKit/UIKit.h>
 
+#import "base/mac/scoped_nsobject.h"
 #import "ios/chrome/browser/ui/animation_util.h"
 #include "ios/chrome/browser/ui/rtl_geometry.h"
 #import "ios/chrome/browser/ui/stack_view/card_view.h"
 #import "ios/chrome/common/material_timing.h"
-
-#if !defined(__has_feature) || !__has_feature(objc_arc)
-#error "This file requires ARC support."
-#endif
 
 using ios::material::TimingFunction;
 
@@ -59,8 +56,8 @@
     const UIEdgeInsets kShadowStretchInsets = {28.0, 28.0, 28.0, 28.0};
     const UIEdgeInsets kShadowLayoutOutset = {-10.0, -11.0, -12.0, -11.0};
     CGRect shadowFrame = UIEdgeInsetsInsetRect(frame, kShadowLayoutOutset);
-    UIImageView* frameShadowImageView =
-        [[UIImageView alloc] initWithFrame:shadowFrame];
+    base::scoped_nsobject<UIImageView> frameShadowImageView(
+        [[UIImageView alloc] initWithFrame:shadowFrame]);
     [frameShadowImageView
         setAutoresizingMask:(UIViewAutoresizingFlexibleWidth |
                              UIViewAutoresizingFlexibleHeight)];
@@ -106,7 +103,8 @@
   // Create paper background.
   CGRect paperFrame = CGRectOffset(endFrame, 0, paperOffset);
   paperFrame.size.height -= paperOffset;
-  PaperView* paper = [[PaperView alloc] initWithFrame:paperFrame];
+  base::scoped_nsobject<PaperView> paper(
+      [[PaperView alloc] initWithFrame:paperFrame]);
   [parent insertSubview:paper belowSubview:view];
   [paper addSubview:view];
   [paper setBackgroundColor:isOffTheRecord
@@ -211,7 +209,8 @@
                                             BOOL isPortrait,
                                             void (^completion)(void)) {
   // Create paper background.
-  PaperView* paper = [[PaperView alloc] initWithFrame:CGRectZero];
+  base::scoped_nsobject<PaperView> paper(
+      [[PaperView alloc] initWithFrame:CGRectZero]);
   UIView* parent = [currentPageCard superview];
   [parent insertSubview:paper aboveSubview:currentPageCard];
   CGRect pageBounds = currentPageCard.bounds;