Drop null/undefined check if we already check for IsUndetectable in BuildCompareNil

Drop null/undefined check if we already check for IsUndetectable in BuildCompareNil

Since https://codereview.chromium.org/1683643002/ null and undefined are
also marked as undetectable. If we anyway need to check for that case,
we can drop the null/undefined checks.

BUG=

Committed: https://crrev.com/0fc7b2c41ff1e7437b09b1e03d1c5ab7d72ec30f
Cr-Commit-Position: refs/heads/master@{#33861}

[Toon Verwaest, 2016-02-09 13:26:54]

verwaest@chromium.org changed reviewers:
+ bmeurer@chromium.org

[Toon Verwaest, 2016-02-09 13:26:54]

ptal

[Benedikt Meurer, 2016-02-09 13:49:30]

LGTM

[Toon Verwaest, 2016-02-10 10:06:35]

The CQ bit was checked by verwaest@chromium.org

[commit-bot: I haz the power, 2016-02-10 10:06:46]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1681813004/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1681813004/40001

[commit-bot: I haz the power, 2016-02-10 10:39:55]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2016-02-10 10:40:33]

Description was changed from

==========
Drop null/undefined check if we already check for IsUndetectable in
BuildCompareNil

Since https://codereview.chromium.org/1683643002/ null and undefined are
also marked as undetectable. If we anyway need to check for that case,
we can drop the null/undefined checks.

BUG=
==========

to

==========
Drop null/undefined check if we already check for IsUndetectable in
BuildCompareNil

Since https://codereview.chromium.org/1683643002/ null and undefined are
also marked as undetectable. If we anyway need to check for that case,
we can drop the null/undefined checks.

BUG=

Committed: https://crrev.com/0fc7b2c41ff1e7437b09b1e03d1c5ab7d72ec30f
Cr-Commit-Position: refs/heads/master@{#33861}
==========

[commit-bot: I haz the power, 2016-02-10 10:40:34]

Patchset 3 (id:??) landed as
https://crrev.com/0fc7b2c41ff1e7437b09b1e03d1c5ab7d72ec30f
Cr-Commit-Position: refs/heads/master@{#33861}