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

ios/chrome/browser/ui/settings/utils/content_setting_backed_boolean.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/browser/ui/settings/utils/content_setting_backed_boolean.h"
 
-#import "base/ios/weak_nsobject.h"
 #include "base/scoped_observer.h"
 #include "components/content_settings/core/browser/content_settings_details.h"
 #include "components/content_settings/core/browser/content_settings_observer.h"
 #include "components/content_settings/core/browser/host_content_settings_map.h"
 #include "components/content_settings/core/common/content_settings.h"
 #include "components/content_settings/core/common/content_settings_types.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 @interface ContentSettingBackedBoolean ()
 
 // The ID of the setting in |settingsMap|.
 @property(nonatomic, readonly) ContentSettingsType settingID;
 
 // Whether the boolean value reflects the state of the preference that backs it,
 // or its negation.
 @property(nonatomic, assign, getter=isInverted) BOOL inverted;
 
 // Whether this object is the one modifying the content setting. Used to filter
@@ skipping 91 matching lines @@
 
 - (void)setValue:(BOOL)value {
   ContentSetting setting =
       (self.inverted ^ value) ? CONTENT_SETTING_ALLOW : CONTENT_SETTING_BLOCK;
   self.isModifyingContentSetting = YES;
   settingsMap_->SetDefaultContentSetting(settingID_, setting);
   self.isModifyingContentSetting = NO;
 }
 
 @end