Support vertical centering of multi-line labels.

Support vertical centering of multi-line labels.

Restore naive vertical centering for multi-line Labels.
Restore multi-line label unit test expectations.

Multi-line labels in horizontal box layouts regressed in:
https://chromium.googlesource.com/chromium/src/+/6060457aff422c0202da9fa0ed1f6243394a5fb1

This does not regress the original baseline fix.
See screenshots at http://crbug.com/429595#c17

BUG=429595
TEST=page info bubble, other labels are vertically centered.
R=sky@chromium.org

Committed: https://crrev.com/9a0f2e91d842259250a428b773aab66db096c73b
Cr-Commit-Position: refs/heads/master@{#303526}

[msw, 2014-11-10 19:58:46]

msw@chromium.org changed reviewers:
+ sky@chromium.org

[msw, 2014-11-10 20:00:25]

Hey Scott, please take a look, thanks!

[sky, 2014-11-10 20:06:50]

LGTM

[msw, 2014-11-10 20:07:04]

The CQ bit was checked by msw@chromium.org

[commit-bot: I haz the power, 2014-11-10 20:08:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/712003005/1

[msw, 2014-11-10 20:33:58]

The CQ bit was checked by msw@chromium.org

[commit-bot: I haz the power, 2014-11-10 20:34:49]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/712003005/20001

[commit-bot: I haz the power, 2014-11-10 21:14:40]

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

[commit-bot: I haz the power, 2014-11-10 21:14:41]

Try jobs failed on following builders:
  android_clang_dbg_recipe on tryserver.chromium.linux
(http://build.chromium.org/p/tryserver.chromium.linux/builders/android_clang_d...)

[msw, 2014-11-10 22:27:02]

The CQ bit was checked by msw@chromium.org

[commit-bot: I haz the power, 2014-11-10 22:28:00]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/712003005/20001

[commit-bot: I haz the power, 2014-11-10 22:49:45]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2014-11-10 22:50:15]

Patchset 2 (id:??) landed as
https://crrev.com/9a0f2e91d842259250a428b773aab66db096c73b
Cr-Commit-Position: refs/heads/master@{#303526}