[ObjC ARC] Converts ios/chrome/app:app_internal to ARC.

ios/chrome/app/chrome_overlay_window.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/app/chrome_overlay_window.h"
 
 #include "base/logging.h"
-#import "base/mac/scoped_nsobject.h"
 #import "ios/chrome/browser/crash_report/breakpad_helper.h"
 #import "ios/chrome/browser/metrics/size_class_recorder.h"
 #import "ios/chrome/browser/tabs/tab_model.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 ChromeOverlayWindow () {
-  base::scoped_nsobject<SizeClassRecorder> _recorder;
+  SizeClassRecorder* _recorder;
 }
 
 // Initializes the size class recorder. On iPad iOS 9+, it starts tracking
 // horizontal size class changes. Otherwise, it is a no-op.
 - (void)initializeRecorderIfNeeded;
 
 // Updates the Breakpad report with the current size class on iOS 8+. Otherwise,
 // it's a no-op since size class doesn't exist.
 - (void)updateBreakpad;
 
@@ skipping 15 matching lines @@
   [super awakeFromNib];
   // When creating via a nib, wait to be awoken, as the size class is not
   // reliable before.
   [self initializeRecorderIfNeeded];
   [self updateBreakpad];
 }
 
 - (void)initializeRecorderIfNeeded {
   DCHECK(!_recorder);
   if (IsIPadIdiom()) {
-    _recorder.reset([[SizeClassRecorder alloc]
-        initWithHorizontalSizeClass:self.traitCollection.horizontalSizeClass]);
+    _recorder = [[SizeClassRecorder alloc]
+        initWithHorizontalSizeClass:self.traitCollection.horizontalSizeClass];
     [[NSNotificationCenter defaultCenter]
         addObserver:self
            selector:@selector(pageLoaded:)
                name:kTabModelTabDidFinishLoadingNotification
              object:nil];
   }
 }
 
 - (void)updateBreakpad {
   breakpad_helper::SetCurrentHorizontalSizeClass(
       self.traitCollection.horizontalSizeClass);
 }
 
 - (void)dealloc {
   [[NSNotificationCenter defaultCenter] removeObserver:self];
-  [super dealloc];
 }
 
 #pragma mark - UITraitEnvironment
 
 - (void)traitCollectionDidChange:(UITraitCollection*)previousTraitCollection {
   [super traitCollectionDidChange:previousTraitCollection];
   if (previousTraitCollection.horizontalSizeClass !=
       self.traitCollection.horizontalSizeClass) {
     [_recorder
         horizontalSizeClassDidChange:self.traitCollection.horizontalSizeClass];
     [self updateBreakpad];
   }
 }
 
 #pragma mark - Notification handler
 
 - (void)pageLoaded:(NSNotification*)notification {
   [_recorder pageLoadedWithHorizontalSizeClass:self.traitCollection
                                                    .horizontalSizeClass];
 }
 
 #pragma mark - Testing methods
 
 - (void)unsetSizeClassRecorder {
-  _recorder.reset();
+  _recorder = nil;
 }
 
 @end