[Resources] Add profile-sized assets for the generic placeholder.

[Resources] Add profile-sized assets for the generic placeholder.

The small, non-high res avatars are 38x31px assets, while the large generic
placeholder is a square, which means that when displayed in the profile
editing grid, it looks stretched out.

BUG=438320
Committed: https://crrev.com/c941ac15694723f0e0117ffd70531f623956d46e
Cr-Commit-Position: refs/heads/master@{#312122}

[noms (inactive), 2015-01-13 21:38:37]

noms@chromium.org changed reviewers:
+ mlerman@chromium.org, oshima@chromium.org

[noms (inactive), 2015-01-13 21:38:37]

I added small profile-sized assets for the placeholder avatar so that it isn't
stretched out in chrome://settings. Please take a look.

oshima: assets and chrome/app/theme/theme_resources.grd
mike: the code bits.

Thanks!

[oshima, 2015-01-13 23:07:14]

c/a/theme lgtm

[Mike Lerman, 2015-01-14 01:07:18]

lgtm "the code bits"

[noms (inactive), 2015-01-19 15:02:59]

The CQ bit was checked by noms@chromium.org

[commit-bot: I haz the power, 2015-01-19 15:03:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/854433003/40001

[commit-bot: I haz the power, 2015-01-19 16:06:03]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-01-19 16:06:23]

Patchset 3 (id:??) landed as
https://crrev.com/c941ac15694723f0e0117ffd70531f623956d46e
Cr-Commit-Position: refs/heads/master@{#312122}