Revert of Disable ExternalPopupMenuRemoveTest.RemoveOnChange.

Revert of Disable ExternalPopupMenuRemoveTest.RemoveOnChange. (patchset #1 id:1 of https://codereview.chromium.org/1271223002/ )

Reason for revert:
Reverted Blink r200000.

Original issue's description:
> Disable ExternalPopupMenuRemoveTest.RemoveOnChange.
>
> The behavior was intentionally changed by Blink r200000 [1].
>
> [1] https://src.chromium.org/viewvc/blink?revision=200000&view=revision
>
> BUG=516945
> TBR=keishi@chromium.org,avi@chromium.org
> NOTRY=true
>
> Committed: https://crrev.com/372de78e05c538ae724563ee107e47fbd17498d4
> Cr-Commit-Position: refs/heads/master@{#341867}

TBR=keishi@chromium.org,avi@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=516945
Committed: https://crrev.com/4e91ab8a35b52410b6a1fe7e61e9c8d2a6e6e4b1
Cr-Commit-Position: refs/heads/master@{#341991}

[tkent, 2015-08-05 22:35:34]

Created Revert of Disable ExternalPopupMenuRemoveTest.RemoveOnChange.

[commit-bot: I haz the power, 2015-08-05 22:35:50]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1274813005/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1274813005/1

[commit-bot: I haz the power, 2015-08-05 22:36:56]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-08-05 22:37:32]

Patchset 1 (id:??) landed as
https://crrev.com/4e91ab8a35b52410b6a1fe7e61e9c8d2a6e6e4b1
Cr-Commit-Position: refs/heads/master@{#341991}