Implementing sign-in promo histograms for bookmark

ios/chrome/browser/ui/bookmarks/bookmark_home_tablet_ntp_controller.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_home_tablet_ntp_controller.h"
 
 #include <memory>
 
 #include "base/ios/block_types.h"
 #include "base/logging.h"
@@ skipping 1141 matching lines @@
                                  rootAncestor:rootAncestor];
   [self updatePrimaryMenuItem:menuItem animated:YES];
 }
 
 #pragma mark - NewTabPagePanelProtocol
 
 - (void)reload {
 }
 
 - (void)wasShown {
+  [_folderView wasShown];
 }
 
 - (void)wasHidden {
   [self cachePosition];
+  [_folderView wasHidden];
 }
 
 - (void)dismissModals {
   [self.actionSheetCoordinator stop];
   self.actionSheetCoordinator = nil;
   [self.editViewController dismiss];
 }
 
 - (void)dismissKeyboard {
   // Uses self.view directly instead of going throught self.view to
@@ skipping 100 matching lines @@
 }
 
 - (NSIndexPath*)indexPathForCell:(UICollectionViewCell*)cell {
   DCHECK([self primaryView].collectionView);
   NSIndexPath* indexPath =
       [[self primaryView].collectionView indexPathForCell:cell];
   return indexPath;
 }
 
 @end