Files.app: Make the touch effect of sort button square.

Files.app: Make the touch effect of sort button square.

As mentioned in Issue 480666, touch effect should be square.
However, the newly-added sort button have the circle effect, so this CL fixes it.

BUG=none
TEST=manually

Committed: https://crrev.com/2f5eaca8989774a7cf618ccf96b49ce6dff51a7b
Cr-Commit-Position: refs/heads/master@{#329355}

[fukino, 2015-05-12 03:40:28]

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

[fukino, 2015-05-12 03:40:28]

PTAL. Thanks!

[yawano, 2015-05-12 03:46:10]

lgtm. Thank you!

[fukino, 2015-05-12 04:54:41]

The CQ bit was checked by fukino@chromium.org

[commit-bot: I haz the power, 2015-05-12 04:54:52]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1124403004/1

[commit-bot: I haz the power, 2015-05-12 05:22:33]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-12 05:23:16]

Patchset 1 (id:??) landed as
https://crrev.com/2f5eaca8989774a7cf618ccf96b49ce6dff51a7b
Cr-Commit-Position: refs/heads/master@{#329355}