Migrate EntriesCallback to use simple success/failure callbacks

This CL is a continuation of the effort to simplify the callbacks
implementation in t_p/b/renderer/modules/filesystem/file_system_callbacks.h
At this time, EntriesCallbacks wrapper class is migrated to use
simple (BindOnce) callbacks, one for success, another for failure.

Note that EntriesCallbacks closures did not share the same callback
completion implementation as some other methods that use the templates
in async_callback_helper.h. Additionally, the success callback can be
called more than once for the same object. Hence

1) WTF::BindRepeating is used for EntriesCallbacks::SuccessCallback .
2) The callback completion bodies were inlined (eg
file_system_directory_iterator.cc, directory_reader_sync.cc and

Additionally, that EntriesCallbacks was the last class in file_system_callbacks.h
to be migrated to success/failures callbacks, instead of wrapper classes.
Its switch over to simple callbacks for success/failure closures allowed
the following classes to be removed:

- DirectoryReader::EntriesCallbackHelper and ErrorCallbackHelper.
- DirectoryReaderSync::EntriesCallbackHelper and ErrorCallbackHelper.
- FileSystemDirectoryIterator::EntriesCallbackHelper and ErrorCallbackHelper.
- EntriesCallbacks::OnDidGetEntriesCallback

Follow up tasks:
- Remove ErrorCallbackBase and ScriptErrorCallback altogether.
- Remove the (now) unused ReportError overloads in
  dom_file_system_base.h|cc, dom_file_system.h|cc and
- Experiment with approaches to remove FileSystemCallbacksBase,
 and invoke callbacks from file_system_dispatcher.cc directly.



Change-Id: I3d6505fa49f05a3bd2cd72db69ecb6f7bb983ed0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1532943
Commit-Queue: Antonio Gomes <tonikitoo@igalia.com>
Commit-Queue: Marijn Kruisselbrink <mek@chromium.org>
Auto-Submit: Antonio Gomes <tonikitoo@igalia.com>
Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#643100}
10 files changed