Splitting AuthenticatorImpl into AuthenitcatorCommon.

This CL introduces authenticator_common.cc, which performs most of the functionality in AuthenticatorImpl. This class is meant to reduce code repetition when introducing ChromeInternalAuthenticatorImpl.

See go/authenticator-util and go/autofill-auth-client-dd for more information.

Bug: 941873
Change-Id: Idd3c535714c69146ee5094e201de301d3da41dee
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1522787
Commit-Queue: Manas Verma <manasverma@google.com>
Reviewed-by: Kim Paulhamus <kpaulhamus@chromium.org>
Cr-Commit-Position: refs/heads/master@{#643111}
6 files changed