Enlarge clickable area of the Files.app's butter bar's close action (x).

Enlarge clickable area of the Files.app's butter bar's close action (x).

The previous (x) button was very tiny - 16x16 pixels, which may be too small when using a touchpad.
This patch modifies css so the x button's clickable area is extended to the surrounding paddings. As a result, it is much easier to cancel an operation.
Along the way, simplified css for actions.

TEST=Copy a large file and try to cancel. Also delete to check if Undo link is not broken.
BUG=175950
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=182373

[mtomasz, 2013-02-13 07:36:44]

@yoshiki: PTAL.

[yoshiki, 2013-02-13 07:37:37]

lgtm

[commit-bot: I haz the power, 2013-02-13 07:43:31]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/mtomasz@chromium.org/12218135/1

[commit-bot: I haz the power, 2013-02-13 16:47:09]

Retried try job too often on win7_aura for step(s) browser_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win7_aura&...