Design document is here:

https://docs.google.com/document/d/1kLjnxPnBAX0G6W-3u6OF_VguuJc0pXdgCRVR0z3yn-g/edit

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/bfbe269e9e9240005d8e89b54f27fc969079030d

commit bfbe269e9e9240005d8e89b54f27fc969079030d
Author: Colin Blundell <blundell@chromium.org>
Date: Tue Nov 20 16:16:36 2018

IdentityManager: Introduce AccountsMutator

This CL introduces AccountsMutator, which will support the mutation of
refresh tokens and seeding of account info for the user's Gaia accounts
in the IdentityManager world.

Its design is conceptually similar to that of PrimaryAccountMutator,
although unlike that class it is supported on all platforms. The full
design doc is here:
https://docs.google.com/document/d/1kLjnxPnBAX0G6W-3u6OF_VguuJc0pXdgCRVR0z3yn-g/edit#

This CL does the following:
- Introduces the class
- Implements an initial API and its unittest
- Adds the ability to get the mutator from IdentityManager

Followup CLs will complete the API surface.

Bug:  887870 
Change-Id: Iafc0d365766118ad07eef5038d2257f1630c254e
Reviewed-on: https://chromium-review.googlesource.com/c/1333775
Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
Commit-Queue: Colin Blundell <blundell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609721}
[modify] https://crrev.com/bfbe269e9e9240005d8e89b54f27fc969079030d/services/identity/BUILD.gn
[modify] https://crrev.com/bfbe269e9e9240005d8e89b54f27fc969079030d/services/identity/public/cpp/BUILD.gn
[add] https://crrev.com/bfbe269e9e9240005d8e89b54f27fc969079030d/services/identity/public/cpp/accounts_mutator.cc
[add] https://crrev.com/bfbe269e9e9240005d8e89b54f27fc969079030d/services/identity/public/cpp/accounts_mutator.h
[add] https://crrev.com/bfbe269e9e9240005d8e89b54f27fc969079030d/services/identity/public/cpp/accounts_mutator_unittest.cc
[modify] https://crrev.com/bfbe269e9e9240005d8e89b54f27fc969079030d/services/identity/public/cpp/identity_manager.cc
[modify] https://crrev.com/bfbe269e9e9240005d8e89b54f27fc969079030d/services/identity/public/cpp/identity_manager.h
[modify] https://crrev.com/bfbe269e9e9240005d8e89b54f27fc969079030d/services/identity/public/cpp/identity_manager_unittest.cc

Going to mark this bug fixed as AccountsMutator is introduced. Filling out its API surface is tracked in  crbug.com/907901 .

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c1485520dd0b14725862d7df7bc866e968610848

commit c1485520dd0b14725862d7df7bc866e968610848
Author: Mario Sanchez Prada <mario@igalia.com>
Date: Wed Jan 09 18:41:57 2019

Implement methods to remove accounts in the AccountsMutator's API

This patchset implements the RemoveAccount and RemoveAllAccounts methods
as per the API described in the "Supporting account seeding and refresh
token mutation in Identity Manager" document [1], along with new unit
tests for both of them.

A follow-up CL will implement the remaining methods to add or update
accounts and refresh tokens, once the discussion in [1] is settled.

[1] https://docs.google.com/document/d/1kLjnxPnBAX0G6W-3u6OF_VguuJc0pXdgCRVR0z3yn-g

Bug:  887870 ,  907901 
Change-Id: I827cee4f339dd378b5aefe95b372ad2d115e71cc
Reviewed-on: https://chromium-review.googlesource.com/c/1373828
Commit-Queue: Mario Sanchez Prada <mario@igalia.com>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Colin Blundell <blundell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#621241}
[modify] https://crrev.com/c1485520dd0b14725862d7df7bc866e968610848/services/identity/BUILD.gn
[modify] https://crrev.com/c1485520dd0b14725862d7df7bc866e968610848/services/identity/public/cpp/DEPS
[modify] https://crrev.com/c1485520dd0b14725862d7df7bc866e968610848/services/identity/public/cpp/accounts_mutator.h
[modify] https://crrev.com/c1485520dd0b14725862d7df7bc866e968610848/services/identity/public/cpp/accounts_mutator_impl.cc
[modify] https://crrev.com/c1485520dd0b14725862d7df7bc866e968610848/services/identity/public/cpp/accounts_mutator_impl.h
[modify] https://crrev.com/c1485520dd0b14725862d7df7bc866e968610848/services/identity/public/cpp/accounts_mutator_impl_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b5721fc683c9684d589f482e39e0ba21703cc608

commit b5721fc683c9684d589f482e39e0ba21703cc608
Author: Mario Sanchez Prada <mario@igalia.com>
Date: Mon Jan 14 11:52:43 2019

Implement remaining method from the AccountsMutator's API: AddOrUpdateAccount()

This patchset implements the remaining method as per the API described
in the "Supporting account seeding and refresh token mutation in Identity
Manager" document [1], along with new unit tests to test different use cases.

[1] https://docs.google.com/document/d/1kLjnxPnBAX0G6W-3u6OF_VguuJc0pXdgCRVR0z3yn-g

Bug:  887870 ,  907901 
Change-Id: I906521369775c1844f4dfaaf8154d092c1f38307
Reviewed-on: https://chromium-review.googlesource.com/c/1379952
Commit-Queue: Mario Sanchez Prada <mario@igalia.com>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
Reviewed-by: Colin Blundell <blundell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622427}
[modify] https://crrev.com/b5721fc683c9684d589f482e39e0ba21703cc608/chrome/browser/signin/identity_manager_factory.cc
[modify] https://crrev.com/b5721fc683c9684d589f482e39e0ba21703cc608/services/identity/public/cpp/accounts_mutator.h
[modify] https://crrev.com/b5721fc683c9684d589f482e39e0ba21703cc608/services/identity/public/cpp/accounts_mutator_impl.cc
[modify] https://crrev.com/b5721fc683c9684d589f482e39e0ba21703cc608/services/identity/public/cpp/accounts_mutator_impl.h
[modify] https://crrev.com/b5721fc683c9684d589f482e39e0ba21703cc608/services/identity/public/cpp/accounts_mutator_impl_unittest.cc
[modify] https://crrev.com/b5721fc683c9684d589f482e39e0ba21703cc608/services/identity/public/cpp/identity_test_environment.cc