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

ios/chrome/browser/ui/bookmarks/bookmark_position_cache.mm

 // Copyright 2014 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/bookmarks/bookmark_position_cache.h"
 
 #include <stdint.h>
 
 #include "base/logging.h"
-#include "base/mac/objc_property_releaser.h"
 
 namespace {
 // The current version of the cached position. This number should be incremented
 // each time the NSCoding implementation changes.
 const int kVersion = 2;
 
 // The value 3 was used for items corresponding to managed bookmarks and
 // was removed during the transition from UIWebView to WKWebView.
 const int kMenuItemManaged = 3;
 
@@ skipping 17 matching lines @@
 
 @implementation BookmarkPositionCache
 @synthesize folderId = _folderId;
 @synthesize position = _position;
 @synthesize type = _type;
 
 #pragma mark - Public Constructors
 
 + (BookmarkPositionCache*)cacheForMenuItemFolderWithPosition:(CGFloat)position
                                                     folderId:(int64_t)folderId {
-  return [[[BookmarkPositionCache alloc]
+  return [[BookmarkPositionCache alloc]
       initWithFolderId:folderId
               position:position
-                  type:bookmarks::MenuItemFolder] autorelease];
+                  type:bookmarks::MenuItemFolder];
 }
 
 #pragma mark - Designated Initializer
 
 - (instancetype)initWithFolderId:(int64_t)folderId
                         position:(CGFloat)position
                             type:(bookmarks::MenuItemType)type {
   self = [super init];
   if (self) {
     _folderId = folderId;
@@ skipping 34 matching lines @@
          static_cast<NSUInteger>(self.folderId);
 }
 
 #pragma mark - NSCoding
 
 - (instancetype)initWithCoder:(NSCoder*)coder {
   int version = [coder decodeIntForKey:kVersionKey];
   int typeInt = [coder decodeIntForKey:kTypeKey];
 
   if (version != kVersion) {
-    [self release];
     return nil;
   }
 
   if (!bookmarks::NumberIsValidMenuItemType(typeInt)) {
-    [self release];
     return nil;
   }
 
   if (typeInt == kMenuItemManaged) {
-    [self release];
     return nil;
   }
 
   bookmarks::MenuItemType type = static_cast<bookmarks::MenuItemType>(typeInt);
   return [self initWithFolderId:[coder decodeInt64ForKey:kFolderKey]
                        position:[coder decodeFloatForKey:kPositionKey]
                            type:type];
 }
 
 - (void)encodeWithCoder:(NSCoder*)coder {
   [coder encodeInt:kVersion forKey:kVersionKey];
   [coder encodeInt:static_cast<int>(self.type) forKey:kTypeKey];
   [coder encodeFloat:self.position forKey:kPositionKey];
   [coder encodeInt64:self.folderId forKey:kFolderKey];
 }
 
 @end