libchromeos: Replace scoped_ptr with std::unique_ptr in D-Bus method handlers

Changed callbacks to use std::unique_ptr in D-Bus method handlers instead of
scoped_ptr, now that we can do this with base::Callback.
This eliminates the need to mix scoped_ptr and std::unique_ptr in the same
translation unit.

Sweep the code in the rest of platform2 that used libchromeos's D-Bus framework.

BUG=None
TEST=`FEATURES=test emerge-link libchromeos apmanager attestation buffet chromeos-dbus-bindings`

Change-Id: I50289198ef9ab183d5bc7d0c8cc7a8f53085e5a4
Reviewed-on: https://chromium-review.googlesource.com/267337
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
Trybot-Ready: Alex Vakulenko <avakulenko@chromium.org>
Reviewed-by: Christopher Wiley <wiley@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
4 files changed