Enable Roboto by default for testing purpose.

Reland this CL since the failed test problem cleared.

Enable Roboto by default for testing purpose.

The testing team wants to enable 'Roboto' by default and have real users to help report bugs too.

In this CL 'Roboto' is enabled by default and can be disabled by going to chrome://flags and turn 'disable-roboto-font-ui' to on.

Also modify the OobeWebUITest to make the tests run in full screen, otherwise the tests will fail due to the incorrect layout of supervised user creation UI (based on xiyuan@'s advice).

Also modify the TextDoesntClip (based on asvitkine@'s advice).

BUG=448948
Committed: https://crrev.com/d5f777b7342dfcfb64b8bdd635ec3599303be08a
Cr-Commit-Position: refs/heads/master@{#313845}

[xdai1, 2015-01-29 22:19:37]

xdai@chromium.org changed reviewers:
+ asvitkine@chromium.org, isherman@chromium.org, sadrul@chromium.org

[xdai1, 2015-01-29 22:19:38]

Reland this CL since it was reverted because some test failed. 

Please re-lgtm. Thanks very much and sorry for the inconvenience.

asvitkine@, please take a look at the render_text_unittest.cc file. Thanks!

[Alexei Svitkine (slow), 2015-01-29 22:22:11]

LGTM for render_text_unittest.cc and histograms.xml

[sadrul, 2015-01-29 23:39:16]

lgtm

[xdai1, 2015-01-29 23:48:56]

The CQ bit was checked by xdai@chromium.org

[commit-bot: I haz the power, 2015-01-29 23:50:11]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/867403005/1

[commit-bot: I haz the power, 2015-01-30 00:58:31]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-30 00:59:38]

Patchset 1 (id:??) landed as
https://crrev.com/d5f777b7342dfcfb64b8bdd635ec3599303be08a
Cr-Commit-Position: refs/heads/master@{#313845}