Move ExtensionIconImageTest to extensions_unittests

Move ExtensionIconImageTest to extensions_unittests

It doesn't need to run in Chrome's unit_tests suite.

BUG=397164
TEST=extensions_unittests

Committed: https://crrev.com/843ee06eec3984c6b850906d51d7923ca1f9bee0
Cr-Commit-Position: refs/heads/master@{#293644}

[James Cook, 2014-09-05 20:07:19]

jamescook@chromium.org changed reviewers:
+ rockot@chromium.org

[James Cook, 2014-09-05 20:07:20]

rockot, PTAL (giving yoz a break from these reviews :-)

[Ken Rockot(use gerrit already), 2014-09-05 20:38:28]

woot! lgtm

[James Cook, 2014-09-05 20:52:19]

The CQ bit was checked by jamescook@chromium.org

[commit-bot: I haz the power, 2014-09-05 20:57:12]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/jamescook@chromium.org/546933002/1

[commit-bot: I haz the power, 2014-09-05 22:41:02]

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

[commit-bot: I haz the power, 2014-09-05 22:41:02]

Try jobs failed on following builders:
  mac_chromium_rel_swarming on tryserver.chromium.mac
(http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

[James Cook, 2014-09-05 23:51:53]

The CQ bit was checked by jamescook@chromium.org

[commit-bot: I haz the power, 2014-09-05 23:53:03]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/jamescook@chromium.org/546933002/1

[commit-bot: I haz the power, 2014-09-06 09:14:07]

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

[commit-bot: I haz the power, 2014-09-06 09:14:08]

Exceeded time limit waiting for builds to trigger.

[James Cook, 2014-09-07 00:05:43]

The CQ bit was checked by jamescook@chromium.org

[commit-bot: I haz the power, 2014-09-07 00:06:26]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/jamescook@chromium.org/546933002/1

[commit-bot: I haz the power, 2014-09-07 00:09:19]

Committed patchset #1 (id:1) as 8bb8a909c4e620b3c618ab226afd0f005a0137d4

[commit-bot: I haz the power, 2014-09-10 03:43:39]

Patchset 1 (id:??) landed as
https://crrev.com/843ee06eec3984c6b850906d51d7923ca1f9bee0
Cr-Commit-Position: refs/heads/master@{#293644}