Backport WebKit patch to fix input button paddings

Backport WebKit patch to fix input button paddings

It's a backport of the following patch by zalan@apple.com:
http://trac.webkit.org/changeset/162803

Subpixel Layout: Align <input type="button", submit> etc
(PushButtonPart) top and bottom paddings with <button>

https://bugs.webkit.org/show_bug.cgi?id=127640
Reviewed by Simon Fraser.

<button> sets padding-top: 2px and padding-bottom: 3px as
default values (html.css), while <input type="button"
(submit, etc) has the hardcoded values of 0, 0 and we
center the text using the available space. This results
in different baseline text position in normal cases. This
adjustment puts the <input type='button' rendering back
to the pre-subpixel layout state.

BUG=143304
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=186630

[Jiang Jiang, 2014-12-05 16:43:54]

Robert, do you by any chance know who might want to take a look at this Mac
Theme change?

[Robert Sesek, 2014-12-05 17:01:28]

I've asked tkent@ or thakis@ to review my Mac theme-related patches in the past.

[Jiang Jiang, 2014-12-05 19:05:44]

jiangj@opera.com changed reviewers:
+ thakis@chromium.org

[Jiang Jiang, 2014-12-05 19:05:44]

Nico, do you want to take a look?

[Nico, 2014-12-05 19:33:48]

lgtm!

[Jiang Jiang, 2014-12-05 22:01:08]

The CQ bit was checked by jiangj@opera.com

[commit-bot: I haz the power, 2014-12-05 22:01:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/778833003/120001

[commit-bot: I haz the power, 2014-12-05 23:39:20]

Committed patchset #7 (id:120001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=186630