[Sync] Add ModelTypeStore implementation.

[Sync] Add ModelTypeStore implementation.

In this change I added ModelTypeStoreImpl and ModelTypeStoreBackend
classes. This change only deals with classes initialization and
threading. To make life of reviewer easier I will add actual IO
operations in separate change.

BUG=517663
R=stanisc@chromium.org

Committed: https://crrev.com/0225b0d41f7660539b9b698af5fa1434216c6394
Cr-Commit-Position: refs/heads/master@{#357660}

[pavely, 2015-11-03 01:34:58]

PTAL.

This change is based on Interface change (http://crrev.com/1422083002). Once
Interface change lands I'll rebase this one.

[stanisc, 2015-11-03 18:52:20]

lgtm with a few minor comments.

https://codereview.chromium.org/1421833004/diff/1/sync/internal_api/model_typ...
File sync/internal_api/model_type_store_impl.cc (right):

https://codereview.chromium.org/1421833004/diff/1/sync/internal_api/model_typ...
sync/internal_api/model_type_store_impl.cc:62:
DCHECK(store->CalledOnValidThread());
Why this DCHECK is for the SUCCESS case only?

https://codereview.chromium.org/1421833004/diff/1/sync/internal_api/model_typ...
File sync/internal_api/model_type_store_impl_unittest.cc (right):

https://codereview.chromium.org/1421833004/diff/1/sync/internal_api/model_typ...
sync/internal_api/model_type_store_impl_unittest.cc:45:
base::Bind(&ModelTypeStoreImplTest::OnInitDone, base::Unretained(this)));
Consider making this a helper function on ModelTypeStoreImplTest.

https://codereview.chromium.org/1421833004/diff/1/sync/internal_api/public/mo...
File sync/internal_api/public/model_type_store_impl.h (right):

https://codereview.chromium.org/1421833004/diff/1/sync/internal_api/public/mo...
sync/internal_api/public/model_type_store_impl.h:51: public:
Is this necessary?

[pavely, 2015-11-03 21:38:09]

https://codereview.chromium.org/1421833004/diff/1/sync/internal_api/model_typ...
File sync/internal_api/model_type_store_impl.cc (right):

https://codereview.chromium.org/1421833004/diff/1/sync/internal_api/model_typ...
sync/internal_api/model_type_store_impl.cc:62:
DCHECK(store->CalledOnValidThread());
On 2015/11/03 18:52:20, stanisc wrote:
> Why this DCHECK is for the SUCCESS case only?

You are right. I also forgot that I should reset store in failure case.

https://codereview.chromium.org/1421833004/diff/1/sync/internal_api/model_typ...
File sync/internal_api/model_type_store_impl_unittest.cc (right):

https://codereview.chromium.org/1421833004/diff/1/sync/internal_api/model_typ...
sync/internal_api/model_type_store_impl_unittest.cc:45:
base::Bind(&ModelTypeStoreImplTest::OnInitDone, base::Unretained(this)));
On 2015/11/03 18:52:20, stanisc wrote:
> Consider making this a helper function on ModelTypeStoreImplTest.

Yes, I will change this in the next CL.

https://codereview.chromium.org/1421833004/diff/1/sync/internal_api/public/mo...
File sync/internal_api/public/model_type_store_impl.h (right):

https://codereview.chromium.org/1421833004/diff/1/sync/internal_api/public/mo...
sync/internal_api/public/model_type_store_impl.h:51: public:
On 2015/11/03 18:52:20, stanisc wrote:
> Is this necessary?

I've created empty class as placeholder. It will own lebeldb's WriteBatch in the
next change.

[pavely, 2015-11-03 21:38:12]

The CQ bit was checked by pavely@chromium.org

[pavely, 2015-11-03 21:38:13]

The patchset sent to the CQ was uploaded after l-g-t-m from stanisc@chromium.org
Link to the patchset: https://codereview.chromium.org/1421833004/#ps20001
(title: "Addressing comment.")

[commit-bot: I haz the power, 2015-11-03 21:40:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1421833004/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1421833004/20001

[commit-bot: I haz the power, 2015-11-03 22:42:15]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-11-03 22:43:25]

Patchset 2 (id:??) landed as
https://crrev.com/0225b0d41f7660539b9b698af5fa1434216c6394
Cr-Commit-Position: refs/heads/master@{#357660}