Fix the incorrect font used by buttons in ChromeOS.

Fix the incorrect font used by buttons in ChromeOS.

WebUI should override the default Blink style for buttons so that buttons can be rendered with the correct font.

BUG=448624
TEST=manually checked on devices (Pixel)

Committed: https://crrev.com/8fc0f8118a42de9a52fa98cc8a3f5c9b9efa74d9
Cr-Commit-Position: refs/heads/master@{#314359}

[xdai1, 2015-02-03 01:15:53]

xdai@chromium.org changed reviewers:
+ xiyuan@chromium.org

[xdai1, 2015-02-03 01:15:54]

Please help to review the CL, thanks!

[xiyuan, 2015-02-03 02:14:23]

lgtm

[xdai1, 2015-02-03 03:54:55]

The CQ bit was checked by xdai@chromium.org

[commit-bot: I haz the power, 2015-02-03 03:56:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/896673002/1

[commit-bot: I haz the power, 2015-02-03 05:57:25]

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

[commit-bot: I haz the power, 2015-02-03 05:57:26]

Try jobs failed on following builders:
  win8_chromium_rel on tryserver.chromium.win (None)

[xdai1, 2015-02-03 17:43:18]

The CQ bit was checked by xdai@chromium.org

[commit-bot: I haz the power, 2015-02-03 17:44:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/896673002/1

[commit-bot: I haz the power, 2015-02-03 17:44:55]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-03 17:45:58]

Patchset 1 (id:??) landed as
https://crrev.com/8fc0f8118a42de9a52fa98cc8a3f5c9b9efa74d9
Cr-Commit-Position: refs/heads/master@{#314359}