The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/822cfab0275712dbd7d69673f68a32461b53c1bc

commit 822cfab0275712dbd7d69673f68a32461b53c1bc
Author: maxbogue <maxbogue@chromium.org>
Date: Fri Oct 28 19:58:47 2016

[Sync] Start implementation of migration for USS.

This approach draws data and metadata from the server half of the
directory and injects it into USS as the initial GetUpdates response.

This CL does not actually enable migration in production because
an empty migrator function is passed instead of the real one.

BUG= 658002 

Review-Url: https://codereview.chromium.org/2442583003
Cr-Commit-Position: refs/heads/master@{#428467}

[modify] https://crrev.com/822cfab0275712dbd7d69673f68a32461b53c1bc/components/sync/BUILD.gn
[modify] https://crrev.com/822cfab0275712dbd7d69673f68a32461b53c1bc/components/sync/engine_impl/model_type_registry.cc
[modify] https://crrev.com/822cfab0275712dbd7d69673f68a32461b53c1bc/components/sync/engine_impl/model_type_registry.h
[modify] https://crrev.com/822cfab0275712dbd7d69673f68a32461b53c1bc/components/sync/engine_impl/model_type_registry_unittest.cc
[modify] https://crrev.com/822cfab0275712dbd7d69673f68a32461b53c1bc/components/sync/engine_impl/model_type_worker.cc
[modify] https://crrev.com/822cfab0275712dbd7d69673f68a32461b53c1bc/components/sync/engine_impl/model_type_worker.h
[modify] https://crrev.com/822cfab0275712dbd7d69673f68a32461b53c1bc/components/sync/engine_impl/model_type_worker_unittest.cc
[modify] https://crrev.com/822cfab0275712dbd7d69673f68a32461b53c1bc/components/sync/engine_impl/sync_manager_impl.cc
[modify] https://crrev.com/822cfab0275712dbd7d69673f68a32461b53c1bc/components/sync/engine_impl/sync_scheduler_impl_unittest.cc
[modify] https://crrev.com/822cfab0275712dbd7d69673f68a32461b53c1bc/components/sync/engine_impl/syncer_unittest.cc
[modify] https://crrev.com/822cfab0275712dbd7d69673f68a32461b53c1bc/components/sync/engine_impl/test_entry_factory.cc
[modify] https://crrev.com/822cfab0275712dbd7d69673f68a32461b53c1bc/components/sync/engine_impl/test_entry_factory.h
[add] https://crrev.com/822cfab0275712dbd7d69673f68a32461b53c1bc/components/sync/engine_impl/uss_migrator.cc
[add] https://crrev.com/822cfab0275712dbd7d69673f68a32461b53c1bc/components/sync/engine_impl/uss_migrator.h
[add] https://crrev.com/822cfab0275712dbd7d69673f68a32461b53c1bc/components/sync/engine_impl/uss_migrator_unittest.cc
[modify] https://crrev.com/822cfab0275712dbd7d69673f68a32461b53c1bc/tools/metrics/histograms/histograms.xml

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e776c62ce54b3d743d018585d7383ef6cc5fb1f0

commit e776c62ce54b3d743d018585d7383ef6cc5fb1f0
Author: maxbogue <maxbogue@chromium.org>
Date: Wed Nov 23 23:53:34 2016

[Sync] Let ModelTypeRegistry filter out initial download USS types.

BUG= 658002 

Review-Url: https://codereview.chromium.org/2500223002
Cr-Commit-Position: refs/heads/master@{#434288}

[modify] https://crrev.com/e776c62ce54b3d743d018585d7383ef6cc5fb1f0/components/sync/engine_impl/model_type_registry.cc
[modify] https://crrev.com/e776c62ce54b3d743d018585d7383ef6cc5fb1f0/components/sync/engine_impl/model_type_registry.h
[modify] https://crrev.com/e776c62ce54b3d743d018585d7383ef6cc5fb1f0/components/sync/engine_impl/sync_manager_impl.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/15a108882f342fd75e7dd3522234189924055943

commit 15a108882f342fd75e7dd3522234189924055943
Author: maxbogue <maxbogue@chromium.org>
Date: Thu Jan 05 00:36:40 2017

[Sync] Enable migration from directory to USS.

This change injects the function that actually migrates directory data
and metadata to USS. This process is designed as purely a bandwidth
optimization for users, and reuses the normal initial merge machinery.

BUG= 658002 

Review-Url: https://codereview.chromium.org/2614773003
Cr-Commit-Position: refs/heads/master@{#441529}

[modify] https://crrev.com/15a108882f342fd75e7dd3522234189924055943/components/sync/engine_impl/sync_manager_impl.cc