Removes unnecessary subclassing of BookmarkCollectionView.

ios/chrome/browser/ui/bookmarks/BUILD.gn

 # 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.
 
 source_set("bookmarks") {
   configs += [ "//build/config/compiler:enable_arc" ]
   sources = [
     "bookmark_collection_cells.h",
     "bookmark_collection_cells.mm",
     "bookmark_collection_view.h",
     "bookmark_collection_view.mm",
     "bookmark_collection_view_background.h",
     "bookmark_collection_view_background.mm",
     "bookmark_controller_factory.h",
     "bookmark_controller_factory.mm",
     "bookmark_edit_view_controller.h",
     "bookmark_edit_view_controller.mm",
     "bookmark_elevated_toolbar.h",
     "bookmark_elevated_toolbar.mm",
     "bookmark_extended_button.h",
     "bookmark_extended_button.mm",
-    "bookmark_folder_collection_view.h",
-    "bookmark_folder_collection_view.mm",
     "bookmark_folder_editor_view_controller.h",
     "bookmark_folder_editor_view_controller.mm",
     "bookmark_folder_table_view_cell.h",
     "bookmark_folder_table_view_cell.mm",
     "bookmark_folder_view_controller.h",
     "bookmark_folder_view_controller.mm",
     "bookmark_home_handset_view_controller.h",
     "bookmark_home_handset_view_controller.mm",
     "bookmark_home_primary_view.h",
     "bookmark_home_tablet_ntp_controller.h",
@@ skipping 211 matching lines @@
     "resources/bookmark_white_edit@2x.png",
     "resources/bookmark_white_edit@3x.png",
     "resources/bookmark_white_move.png",
     "resources/bookmark_white_move@2x.png",
     "resources/bookmark_white_move@3x.png",
   ]
   outputs = [
     "{{bundle_resources_dir}}/{{source_file_part}}",
   ]
 }