Update frame around SAML IdP pages to new GAIA style

Update frame around SAML IdP pages to new GAIA style

This CL updates the window in which SAML IdP pages are shown to match
the new GAIA style:
* The window expands to the size requested in the mocks.
* The header text is updated to match the mocks.
* An "X" button is shown, as requested in the mocks.

The CL updates the windows shown during login and enrollment. Both are
bit-for-bit identical now. See the bug for screen shots.

BUG=467167
TEST=Manual

Committed: https://crrev.com/7c02446724730577cf687e904b116b20027eb558
Cr-Commit-Position: refs/heads/master@{#325409}

[bartfab (slow), 2015-04-15 11:53:48]

bartfab@chromium.org changed reviewers:
+ dzhioev@chromium.org

[bartfab (slow), 2015-04-15 11:53:48]

Hi Pavel,

Could you take a look please?

[Nikita (slow), 2015-04-15 14:39:23]

nkostylev@chromium.org changed reviewers:
+ nkostylev@chromium.org
- dzhioev@chromium.org

[Nikita (slow), 2015-04-15 14:41:21]

Per discussion with Pavel, rebalancing his CL review load a bit.

I'm taking this one.

[Nikita (slow), 2015-04-16 08:32:38]

lgtm

[bartfab (slow), 2015-04-16 09:13:15]

The CQ bit was checked by bartfab@chromium.org

[commit-bot: I haz the power, 2015-04-16 09:13:49]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1052103003/1

[commit-bot: I haz the power, 2015-04-16 09:42:56]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-16 09:43:56]

Patchset 1 (id:??) landed as
https://crrev.com/7c02446724730577cf687e904b116b20027eb558
Cr-Commit-Position: refs/heads/master@{#325409}