Remove unused icon assets from theme_resources.grd.

Remove unused icon assets from theme_resources.grd.

Now that Files.app has own file-type icons with Material Design, many icons in
theme_resources.grd are not in use.

BUG=none
TEST=full build and run browser_tests

Committed: https://crrev.com/a3a9430ea607e75f645636fc1e97146870c7ff29
Cr-Commit-Position: refs/heads/master@{#317743}

[fukino, 2015-02-20 03:54:31]

fukino@chromium.org changed reviewers:
+ mtomasz@chromium.org, oshima@chromium.org

[fukino, 2015-02-20 03:54:32]

oshima@: PTAL at chrome/app/theme.
mtomasz@: PTAL at ui/file_manager. It seems [file-type-icon='drive'] is not in
use.

[mtomasz, 2015-02-20 05:07:03]

lgtm

[oshima, 2015-02-24 01:10:54]

lgtm

[fukino, 2015-02-24 01:58:15]

The CQ bit was checked by fukino@chromium.org

[commit-bot: I haz the power, 2015-02-24 01:59:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/937373002/1

[commit-bot: I haz the power, 2015-02-24 02:20:55]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-24 02:21:53]

Patchset 1 (id:??) landed as
https://crrev.com/a3a9430ea607e75f645636fc1e97146870c7ff29
Cr-Commit-Position: refs/heads/master@{#317743}