Update bookmark bar folder icons to MD; vectorize.

Update bookmark bar folder icons to MD; vectorize.

IDR_BOOKMARK_BAR_FOLDER is not yet deleted because it's still used in
chrome://bookmarks.

BUG=505953
Committed: https://crrev.com/14415067eb5131fd93aa1096b42e2a38c97b6657
Cr-Commit-Position: refs/heads/master@{#346733}

[Evan Stade, 2015-09-01 19:10:50]

estade@chromium.org changed reviewers:
+ sky@chromium.org

[Evan Stade, 2015-09-01 19:10:50]

This doesn't look so great on the bm bar on a dark theme, but then again a lot
of favicons don't. I'll try to address that in a follow up.

[sky, 2015-09-01 20:36:23]

LGTM

[Evan Stade, 2015-09-01 20:41:25]

The CQ bit was checked by estade@chromium.org

[commit-bot: I haz the power, 2015-09-01 20:41:37]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1319213004/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1319213004/40001

[commit-bot: I haz the power, 2015-09-01 20:58:44]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-09-01 20:59:25]

Patchset 3 (id:??) landed as
https://crrev.com/14415067eb5131fd93aa1096b42e2a38c97b6657
Cr-Commit-Position: refs/heads/master@{#346733}