Gallery: Fix scrolling by touch in the mosaic view.

Gallery: Fix scrolling by touch in the mosaic view.

We cannot scroll the mosaic view by touching since crrev.com/283688.
The touch event is covered by other elements. pointe-events:none does not help
to make it scrollable by touch.

BUG=404960
TEST=test scrolling on link

Committed: https://crrev.com/0da5098d7e901bef3770f316c44e480e7087803d
Cr-Commit-Position: refs/heads/master@{#293281}

[hirono, 2014-09-03 13:12:54]

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

[hirono, 2014-09-03 13:12:54]

PTAL the CL? Thank you!

[fukino, 2014-09-04 03:28:35]

The CQ bit was checked by fukino@chromium.org

[fukino, 2014-09-04 03:28:38]

The CQ bit was unchecked by fukino@chromium.org

[fukino, 2014-09-04 03:28:43]

On 2014/09/03 13:12:54, hirono wrote:
> PTAL the CL? Thank you!

lgtm!

[hirono, 2014-09-04 03:39:56]

The CQ bit was checked by hirono@chromium.org

[commit-bot: I haz the power, 2014-09-04 03:40:41]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/hirono@chromium.org/535673004/1

[commit-bot: I haz the power, 2014-09-04 07:32:09]

Committed patchset #1 (id:1) as bb6eb95d5d4c9ba0a2c3a24a168359c62d67ab95

[commit-bot: I haz the power, 2014-09-10 03:30:43]

Patchset 1 (id:??) landed as
https://crrev.com/0da5098d7e901bef3770f316c44e480e7087803d
Cr-Commit-Position: refs/heads/master@{#293281}