[Local NTP] block image-related context menu items for thumbnails; CSS fixes.

[Local NTP] block image-related context menu items for thumbnails; CSS fixes.

In https://chromiumcodereview.appspot.com/473583002/ we removed a
'shadow' element in thumbnail <iframe> to improve customization. A side
effect is that this exposes the thumbnail image, thereby alow the user
to futilely access the chrome-search://thumb/#/# image below. This CL
adds back a transparent "blocker" in front of the thumbnail to restore
old behavior. Also making 2 CSS changes to:
- Fix fake box text positioning for RTL.
- Move top-margin back from #ntp-contents to #logo, for correctness.

BUG=411005
Committed: https://crrev.com/552e4158d943c8d5ab58e8fe69d019f5583724c4
Cr-Commit-Position: refs/heads/master@{#293650}

[huangs, 2014-09-05 05:01:37]

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

[huangs, 2014-09-05 05:01:37]

PTAL.

[Mathieu, 2014-09-05 15:10:01]

lgtm

[Mathieu, 2014-09-05 15:10:13]

The CQ bit was checked by mathp@chromium.org

[Mathieu, 2014-09-05 15:10:14]

The CQ bit was unchecked by mathp@chromium.org

[Mathieu, 2014-09-05 15:10:14]

The CQ bit was checked by mathp@chromium.org

[commit-bot: I haz the power, 2014-09-05 15:11:03]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/huangs@chromium.org/542033002/1

[commit-bot: I haz the power, 2014-09-05 15:20:42]

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

[commit-bot: I haz the power, 2014-09-05 15:20:43]

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

[huangs, 2014-09-06 06:49:39]

The CQ bit was checked by huangs@chromium.org

[commit-bot: I haz the power, 2014-09-06 06:50:29]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/huangs@chromium.org/542033002/1

[commit-bot: I haz the power, 2014-09-06 06:51:50]

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

[commit-bot: I haz the power, 2014-09-06 06:51:51]

Failed to apply the patch.

[huangs, 2014-09-06 13:45:17]

The CQ bit was checked by huangs@chromium.org

[commit-bot: I haz the power, 2014-09-06 13:45:52]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/huangs@chromium.org/542033002/20001

[commit-bot: I haz the power, 2014-09-06 15:46:48]

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

[commit-bot: I haz the power, 2014-09-06 15:46:49]

Exceeded time limit waiting for builds to trigger.

[huangs, 2014-09-07 03:28:45]

The CQ bit was checked by huangs@chromium.org

[commit-bot: I haz the power, 2014-09-07 03:29:15]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/huangs@chromium.org/542033002/20001

[commit-bot: I haz the power, 2014-09-07 03:30:20]

Committed patchset #2 (id:20001) as 6b3c2817763229771d2bcabf9d6f96b14a42ece6

[commit-bot: I haz the power, 2014-09-10 03:43:51]

Patchset 2 (id:??) landed as
https://crrev.com/552e4158d943c8d5ab58e8fe69d019f5583724c4
Cr-Commit-Position: refs/heads/master@{#293650}