DCHECK that ProfileSyncService is created on the UI thread.

DCHECK that ProfileSyncService is created on the UI thread.

An unrelated change of mine revealed that SyncBackendMigratorTest
failed to correctly initialize the browser threads necessary for
creating ProfileSyncService.

This error manifested in a confusing way, so I've added a DCHECK to
make it clearer in the future.

Committed: https://crrev.com/82d4e4f35960e443e9eb56a84bd4121ce9140586
Cr-Commit-Position: refs/heads/master@{#316882}

[maxbogue, 2015-02-18 01:23:23]

maxbogue@chromium.org changed reviewers:
+ maniscalco@chromium.org

[maxbogue, 2015-02-18 01:23:24]

PTAL!

[maniscalco, 2015-02-18 17:03:00]

LGTM with one nit...

https://codereview.chromium.org/936673002/diff/1/chrome/browser/sync/backend_...
File chrome/browser/sync/backend_migrator_unittest.cc (right):

https://codereview.chromium.org/936673002/diff/1/chrome/browser/sync/backend_...
chrome/browser/sync/backend_migrator_unittest.cc:106:
content::TestBrowserThreadBundle thread_bundle_;
nit: can you see about making thread_bundle_ the first data member?  I.e. swap
this line with the one above it.  Generally, you want your message loops to be
the first things created and the last ones destroyed in tests.  Actually, is
snap_ used anywhere?  Maybe you can just delete it.

[maxbogue, 2015-02-18 18:58:14]

New patchsets have been uploaded after l-g-t-m from maniscalco@chromium.org

[maxbogue, 2015-02-18 19:00:06]

https://codereview.chromium.org/936673002/diff/1/chrome/browser/sync/backend_...
File chrome/browser/sync/backend_migrator_unittest.cc (right):

https://codereview.chromium.org/936673002/diff/1/chrome/browser/sync/backend_...
chrome/browser/sync/backend_migrator_unittest.cc:106:
content::TestBrowserThreadBundle thread_bundle_;
On 2015/02/18 17:03:00, maniscalco wrote:
> nit: can you see about making thread_bundle_ the first data member?  I.e. swap
> this line with the one above it.  Generally, you want your message loops to be
> the first things created and the last ones destroyed in tests.  Actually, is
> snap_ used anywhere?  Maybe you can just delete it. 

Deleted it and the tests still pass.

[maxbogue, 2015-02-18 19:00:09]

The CQ bit was checked by maxbogue@chromium.org

[commit-bot: I haz the power, 2015-02-18 19:01:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/936673002/20001

[commit-bot: I haz the power, 2015-02-18 20:19:22]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-02-18 20:20:04]

Patchset 2 (id:??) landed as
https://crrev.com/82d4e4f35960e443e9eb56a84bd4121ce9140586
Cr-Commit-Position: refs/heads/master@{#316882}