Files.app: Do not run thumbnail fetch during directory scan.

Files.app: Do not run thumbnail fetch during directory scan.

In order not to block IO of directory scan by IO of thumbnail fetch,
do not run thumbnail fetch when directory scan is running.

BUG=470462
TEST=out/Release/browser_tests --gtest_filter=FileManagerJsTest.ListThumbnailLoader

Committed: https://crrev.com/ee41ade513464f548961a22e313a6177558adcce
Cr-Commit-Position: refs/heads/master@{#322330}

[yawano, 2015-03-26 05:24:35]

yawano@chromium.org changed reviewers:
+ fukino@chromium.org

[yawano, 2015-03-26 05:24:35]

PTAL. Thank you!

[fukino, 2015-03-26 05:46:17]

lgtm. Thanks!

[yawano, 2015-03-26 05:46:48]

On 2015/03/26 05:46:17, fukino wrote:
> lgtm. Thanks!

Thank you!

[yawano, 2015-03-26 05:46:53]

The CQ bit was checked by yawano@chromium.org

[commit-bot: I haz the power, 2015-03-26 05:47:11]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1031293005/1

[commit-bot: I haz the power, 2015-03-26 05:53:57]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-26 05:55:01]

Patchset 1 (id:??) landed as
https://crrev.com/ee41ade513464f548961a22e313a6177558adcce
Cr-Commit-Position: refs/heads/master@{#322330}