Revert of [Sync] Stop accessing BrowserContextKeyedServiceFactory on non-UI thread.

Revert of [Sync] Stop accessing BrowserContextKeyedServiceFactory on non-UI thread. (patchset #8 id:140001 of https://codereview.chromium.org/2769113002/ )

Reason for revert:
Caused a memory regression, see crbug.com/708666 , unclear to me why exactly this is. Progress investigating the memory regression seems tricky so far, so reverting to fix more quickly.

Original issue's description:
> [Sync] Stop accessing BrowserContextKeyedServiceFactory on non-UI thread.
> 
> In the past the AsyncDirectoryTypeController was passing a raw pointer
> to a ChromeSyncClient to the model thread, where it had
> GetSyncableServiceForType called on it. This was needed for several
> model types, which has specific logic around only accessing their
> SyncableService on their model threads. However, this was also bad, as
> BrowserContextKeyedServiceFactorys were being used with a Profile
> object on a non-UI thread, which is against the rules.
> 
> To fix this, GetSyncableServiceForType returns a callback which should
> only be run on the model thread, that will return the same
> WeakPtr<SyncableService> that we were used to. The various non-UI
> thread model types do slightly different things as each type has
> different rules and threading guarantees.
> 
> The most involved model type in this CL was extensions, which did not
> have sufficient threading constraints to ensure safety. Added weak
> pointer support to SyncValueStoreCache to fix this.
> 
> BUG=701326
> 
> Review-Url: https://codereview.chromium.org/2769113002
> Cr-Commit-Position: refs/heads/master@{#460304}
> Committed: https://chromium.googlesource.com/chromium/src/+/cd6b31d4b9613087e1a68c620af83b6fe1892bdf

TBR=pavely@chromium.org,rdevlin.cronin@chromium.org,mathp@chromium.org,vasilii@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=701326
Review-Url: https://codereview.chromium.org/2799653006
Cr-Commit-Position: refs/heads/master@{#462578}
Committed: https://chromium.googlesource.com/chromium/src/+/a56dd49ba64abaf5300e5ccd8874447821e53da1

[skym, 2017-04-06 17:08:43]

The CQ bit was checked by skym@chromium.org

[skym, 2017-04-06 17:08:44]

Created Revert of [Sync] Stop accessing BrowserContextKeyedServiceFactory on
non-UI thread.

[commit-bot: I haz the power, 2017-04-06 17:09:17]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-04-06 19:20:33]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1491498523659310, "parent_rev":
"e4e3e7e4169e07176f674d94bbcc99f2392e927d", "commit_rev":
"a56dd49ba64abaf5300e5ccd8874447821e53da1"}

[commit-bot: I haz the power, 2017-04-06 19:21:23]

Description was changed from

==========
Revert of [Sync] Stop accessing BrowserContextKeyedServiceFactory on non-UI
thread. (patchset #8 id:140001 of https://codereview.chromium.org/2769113002/ )

Reason for revert:
Caused a memory regression, see crbug.com/708666 , unclear to me why exactly
this is. Progress investigating the memory regression seems tricky so far, so
reverting to fix more quickly.

Original issue's description:
> [Sync] Stop accessing BrowserContextKeyedServiceFactory on non-UI thread.
> 
> In the past the AsyncDirectoryTypeController was passing a raw pointer
> to a ChromeSyncClient to the model thread, where it had
> GetSyncableServiceForType called on it. This was needed for several
> model types, which has specific logic around only accessing their
> SyncableService on their model threads. However, this was also bad, as
> BrowserContextKeyedServiceFactorys were being used with a Profile
> object on a non-UI thread, which is against the rules.
> 
> To fix this, GetSyncableServiceForType returns a callback which should
> only be run on the model thread, that will return the same
> WeakPtr<SyncableService> that we were used to. The various non-UI
> thread model types do slightly different things as each type has
> different rules and threading guarantees.
> 
> The most involved model type in this CL was extensions, which did not
> have sufficient threading constraints to ensure safety. Added weak
> pointer support to SyncValueStoreCache to fix this.
> 
> BUG=701326
> 
> Review-Url: https://codereview.chromium.org/2769113002
> Cr-Commit-Position: refs/heads/master@{#460304}
> Committed:
https://chromium.googlesource.com/chromium/src/+/cd6b31d4b9613087e1a68c620af8...

TBR=pavely@chromium.org,rdevlin.cronin@chromium.org,mathp@chromium.org,vasili...
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=701326
==========

to

==========
Revert of [Sync] Stop accessing BrowserContextKeyedServiceFactory on non-UI
thread. (patchset #8 id:140001 of https://codereview.chromium.org/2769113002/ )

Reason for revert:
Caused a memory regression, see crbug.com/708666 , unclear to me why exactly
this is. Progress investigating the memory regression seems tricky so far, so
reverting to fix more quickly.

Original issue's description:
> [Sync] Stop accessing BrowserContextKeyedServiceFactory on non-UI thread.
> 
> In the past the AsyncDirectoryTypeController was passing a raw pointer
> to a ChromeSyncClient to the model thread, where it had
> GetSyncableServiceForType called on it. This was needed for several
> model types, which has specific logic around only accessing their
> SyncableService on their model threads. However, this was also bad, as
> BrowserContextKeyedServiceFactorys were being used with a Profile
> object on a non-UI thread, which is against the rules.
> 
> To fix this, GetSyncableServiceForType returns a callback which should
> only be run on the model thread, that will return the same
> WeakPtr<SyncableService> that we were used to. The various non-UI
> thread model types do slightly different things as each type has
> different rules and threading guarantees.
> 
> The most involved model type in this CL was extensions, which did not
> have sufficient threading constraints to ensure safety. Added weak
> pointer support to SyncValueStoreCache to fix this.
> 
> BUG=701326
> 
> Review-Url: https://codereview.chromium.org/2769113002
> Cr-Commit-Position: refs/heads/master@{#460304}
> Committed:
https://chromium.googlesource.com/chromium/src/+/cd6b31d4b9613087e1a68c620af8...

TBR=pavely@chromium.org,rdevlin.cronin@chromium.org,mathp@chromium.org,vasili...
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=701326

Review-Url: https://codereview.chromium.org/2799653006
Cr-Commit-Position: refs/heads/master@{#462578}
Committed:
https://chromium.googlesource.com/chromium/src/+/a56dd49ba64abaf5300e5ccd8874...
==========

[commit-bot: I haz the power, 2017-04-06 19:21:25]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/a56dd49ba64abaf5300e5ccd8874...