Replace single-threaded SequencedWorkerPool with base::Thread in WallpaperResizerTest.

Replace single-threaded SequencedWorkerPool with base::Thread in WallpaperResizerTest.

Also while here:
 - const scoped_refptr<>& => scoped_refptr<> + std::move
   (helps avoiding unnecessary refcount bumps:
    https://groups.google.com/a/chromium.org/d/topic/chromium-dev/TlL1D-Djta0/discussion)

BUG=646443
Committed: https://crrev.com/2525299ceb48722a1271c8c7e8ae1bbd8aa724e3
Cr-Commit-Position: refs/heads/master@{#418855}

[gab, 2016-09-14 18:52:02]

The CQ bit was checked by gab@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-09-14 18:52:44]

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

[gab, 2016-09-14 18:53:03]

gab@chromium.org changed reviewers:
+ bshe@chromium.org

[gab, 2016-09-14 18:53:04]

@bshe PTAL, thanks!

CC msw FYI per new scoped_refptr style cleanup following
https://codereview.chromium.org/2318223003

[msw, 2016-09-14 18:56:35]

msw@chromium.org changed reviewers:
+ msw@chromium.org

[msw, 2016-09-14 18:56:36]

Thanks for cleaning up after my ignorance.

[commit-bot: I haz the power, 2016-09-14 20:06:45]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-09-14 20:06:46]

Dry run: This issue passed the CQ dry run.

[bshe, 2016-09-15 13:23:05]

On 2016/09/14 18:56:36, msw wrote:
> Thanks for cleaning up after my ignorance.

lgtm

[gab, 2016-09-15 13:30:35]

The CQ bit was checked by gab@chromium.org

[commit-bot: I haz the power, 2016-09-15 13:30:51]

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, 2016-09-15 13:36:02]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-09-15 13:39:24]

Description was changed from

==========
Replace single-threaded SequencedWorkerPool with base::Thread in
WallpaperResizerTest.

Also while here:
 - const scoped_refptr<>& => scoped_refptr<> + std::move
   (helps avoiding unnecessary refcount bumps:
   
https://groups.google.com/a/chromium.org/d/topic/chromium-dev/TlL1D-Djta0/dis...)

BUG=646443
==========

to

==========
Replace single-threaded SequencedWorkerPool with base::Thread in
WallpaperResizerTest.

Also while here:
 - const scoped_refptr<>& => scoped_refptr<> + std::move
   (helps avoiding unnecessary refcount bumps:
   
https://groups.google.com/a/chromium.org/d/topic/chromium-dev/TlL1D-Djta0/dis...)

BUG=646443

Committed: https://crrev.com/2525299ceb48722a1271c8c7e8ae1bbd8aa724e3
Cr-Commit-Position: refs/heads/master@{#418855}
==========

[commit-bot: I haz the power, 2016-09-15 13:39:24]

Patchset 1 (id:??) landed as
https://crrev.com/2525299ceb48722a1271c8c7e8ae1bbd8aa724e3
Cr-Commit-Position: refs/heads/master@{#418855}