[ios] Hides native navigationBar on legacyBookmarks Editors.

- self.navigationController.navigationBarHidden = YES; wasn't being set or propagated to these VC's
anymore. This causes both the native navBar and MDCAppBar to be added to the view hierarchy.

On top of making tests fail, there was a large top inset on legacy Editors added by the native
navBar.

Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I3b5196516c7b9c242cfef4ef89a01299c2ae0087
Reviewed-on: https://chromium-review.googlesource.com/1103295
Commit-Queue: Rohit Rao <rohitrao@chromium.org>
Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567822}

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

@@ -218,6 +218,7 @@ typedef NS_ENUM(NSInteger, ItemType) {
         setSeparatorInset:UIEdgeInsetsMake(
                               0, kBookmarkCellHorizontalLeadingInset, 0, 0)];
   } else {
+    self.navigationController.navigationBarHidden = YES;
     [self.tableView setSeparatorStyle:UITableViewCellSeparatorStyleNone];
   }
 

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

@@ -179,6 +179,7 @@ folderEditorWithBookmarkModel:(bookmarks::BookmarkModel*)bookmarkModel
         setSeparatorInset:UIEdgeInsetsMake(
                               0, kBookmarkCellHorizontalLeadingInset, 0, 0)];
   } else {
+    self.navigationController.navigationBarHidden = YES;
     [self.tableView setSeparatorStyle:UITableViewCellSeparatorStyleNone];
   }