Factor out remote changes from ClientTagBasedModelTypeProcessor.

Move OnIncrementalUpdate to separate class ClientTagBasedUpdateHandler.
There is no behavioral changes, mostly mechanical move incremental
update logic. This is only first step, in the next steps dependencies
from ClientTagBasedModelTypeProcessor internal fields will be replaced.

Bug: 947044
Change-Id: Id25d856166ac51035cca731e9ab142c94c583258
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1978685
Commit-Queue: Rushan Suleymanov <rushans@google.com>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#728866}
7 files changed