Change the default font size in ChromeOS from 12px to 13px.

Based on UI designer folks requirement, change the default font size in ChromeOS from 12px to 13px.

BUG=449675
TEST=zha@, sgabriel@ manually checked on devices (1x, 2x)

Committed: https://crrev.com/ad46c41ecb9cb2afb6a7e535e36679d84691f70e
Cr-Commit-Position: refs/heads/master@{#314363}

[xdai1, 2015-01-31 00:18:12]

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

[xdai1, 2015-01-31 00:18:39]

Please take a look at the CL, thanks!

[sadrul, 2015-02-03 02:46:09]

lgtm

[xdai1, 2015-02-03 03:55:11]

The CQ bit was checked by xdai@chromium.org

[commit-bot: I haz the power, 2015-02-03 03:56:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/887153002/1

[commit-bot: I haz the power, 2015-02-03 05:57:23]

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

[commit-bot: I haz the power, 2015-02-03 05:57:24]

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

[xdai1, 2015-02-03 17:48:31]

The CQ bit was checked by xdai@chromium.org

[commit-bot: I haz the power, 2015-02-03 17:49:13]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/887153002/1

[commit-bot: I haz the power, 2015-02-03 17:50:08]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-03 17:51:03]

Patchset 1 (id:??) landed as
https://crrev.com/ad46c41ecb9cb2afb6a7e535e36679d84691f70e
Cr-Commit-Position: refs/heads/master@{#314363}