Gallery.app: Fix thumbnail update of the ribbon in the slide mode.

Gallery.app: Fix thumbnail update of the ribbon in the slide mode.

Previously Gallery.app tried to create a new element when an image is updated,
but the new element does not added to DOM.

This CL change the behavior so that the app reuses an existing element.

BUG=385535
TEST=manually

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=278405

[hirono, 2014-06-19 05:00:31]

PTAL the CL? Thank you!

[yoshiki, 2014-06-19 10:37:50]

lgtm

[hirono, 2014-06-19 11:12:00]

The CQ bit was checked by hirono@chromium.org

[commit-bot: I haz the power, 2014-06-19 11:14:44]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/hirono@chromium.org/343873002/20001

[commit-bot: I haz the power, 2014-06-19 15:48:23]

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

[commit-bot: I haz the power, 2014-06-19 15:48:24]

Try jobs failed on following builders:
  win_gpu_triggered_tests on tryserver.chromium.gpu
(http://build.chromium.org/p/tryserver.chromium.gpu/builders/win_gpu_triggered...)

[hirono, 2014-06-19 16:43:13]

The CQ bit was checked by hirono@chromium.org

[commit-bot: I haz the power, 2014-06-19 16:45:20]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/hirono@chromium.org/343873002/20001

[commit-bot: I haz the power, 2014-06-19 16:52:55]

Change committed as 278405