Explicitly use CompletionRepeatingCallback in //c/b/cache_storage

There are cases where base::AdaptCallbackForRepeating() needs to be used
in cache_storage_blob_to_disk_cache.cc and cache_storage_cache.cc to
adapt OnceCallback callbacks so that they can run either right after
invoking the operation at hand (when rv != net::ERR_IO_PENDING), from the
same calling function, or once the asynchronous operation has been completed.

In these cases, let's explicitly declare those adapted callbacks as repeating
ones instead of using CompletionCallback, which will eventually be changed to
alias CompletionOnceCallback instead of CompletionRepeatingCallback.

Bug: 714018, 807724
Change-Id: Iacf223b439fdce99bae429fb5f62ad58f63169fc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1528242
Commit-Queue: Mario Sanchez Prada <mario@igalia.com>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Reviewed-by: Bence Béky <bnc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#642552}
2 files changed