[ios] Fix "return foo = nil" introduced by ARC conversion tools.

ios/chrome/browser/ui/tab_switcher/tab_switcher_panel_cell.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/browser/ui/tab_switcher/tab_switcher_panel_cell.h"
 
 #import "ios/chrome/browser/tabs/tab.h"
 #import "ios/chrome/browser/ui/fade_truncated_label.h"
 #import "ios/chrome/browser/ui/image_util.h"
 #import "ios/chrome/browser/ui/tab_switcher/tab_switcher_button.h"
@@ skipping 296 matching lines @@
 #pragma mark - UIAccessibilityAction
 
 - (NSArray*)accessibilityCustomActions {
   NSMutableArray* customActions = [[NSMutableArray alloc] init];
   UIAccessibilityCustomAction* customAction =
       [[UIAccessibilityCustomAction alloc]
           initWithName:l10n_util::GetNSString(IDS_IOS_TAB_SWITCHER_CLOSE_TAB)
                 target:self
               selector:@selector(closeButtonPressed)];
   [customActions addObject:customAction = nil];
-  return customActions = nil;
+  return customActions;
 }
 
 @end
 
 @implementation TabSwitcherDistantSessionCell {
   UILabel* _titleLabel;
   UIImageView* _favicon;
   UIImageView* _newTabIcon;
   UIView* _verticallyCenteredView;
   TabSwitcherButton* _raisedButton;
@@ skipping 124 matching lines @@
 - (void)prepareForReuse {
   [_newTabIcon setAlpha:0];
   [_faviconObtainer cancel];
   _faviconObtainer = nil;
   [_raisedButton setAlpha:0];
   [_raisedButton resetState];
   [super prepareForReuse];
 }
 
 @end