Removed unused callback |shared_url_loader_factory_getter_| from GCMS

This repeating callback got introduced along with crrev.com/c/1630162
but it's not used anywhere, so let's remove it.

Bug: 939372
Change-Id: I772d7c766da0669b4b11fa55a77e7adbb3c483cb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1660445
Reviewed-by: Colin Blundell <blundell@chromium.org>
Reviewed-by: Lowell Manners <lowell@chromium.org>
Commit-Queue: Mario Sanchez Prada <mario@igalia.com>
Cr-Commit-Position: refs/heads/master@{#669595}
1 file changed