[Local NTP] Fixing thumbnail aspect ratio, and store taller thumbnails.

[Local NTP] Fixing thumbnail aspect ratio, and store taller thumbnails.

Previously the local NTP thumbnails were stretched. We now make preserve
ratio preserved by setting height to "auto", but keep min-height to 100%
so if thumbnail is too short we won't see blank space.
To accommotate Material Design thumbnails, we make stored thumbnails
taller. In the thumbnail <iframe>, the extra height is hidden from view.

BUG=414878
Committed: https://crrev.com/f93d5878812464ccb22dde80d35234d37accc338
Cr-Commit-Position: refs/heads/master@{#295155}

[huangs, 2014-09-16 20:09:29]

huangs@chromium.org changed reviewers:
+ jhawkins@chromium.org

[huangs, 2014-09-16 20:09:30]

PTAL simple change.

Do you think thumbnails should also be made wider? We are changing 138 x 83
thumbnail to 148 x 94.

[James Hawkins, 2014-09-16 20:29:26]

LGTM

I don't have enough context to answer your question, though.

[huangs, 2014-09-16 20:39:00]

I think it's okay to keep the size; just wondering if you'd prefer otherwise. 
Submitting.

[huangs, 2014-09-16 20:39:36]

Thanks!

[huangs, 2014-09-16 20:39:42]

The CQ bit was checked by huangs@chromium.org

[commit-bot: I haz the power, 2014-09-16 20:40:12]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/564973003/20001

[commit-bot: I haz the power, 2014-09-16 22:05:36]

Committed patchset #2 (id:20001) as 6702725b22556b6c521249c25eaae529e4f7c3b1

[commit-bot: I haz the power, 2014-09-16 22:06:07]

Patchset 2 (id:??) landed as
https://crrev.com/f93d5878812464ccb22dde80d35234d37accc338
Cr-Commit-Position: refs/heads/master@{#295155}