Reland of [turbofan] Insert dummy values when changing from None type.

Reland of [turbofan] Insert dummy values when changing from None type.

This reverts commit a55fdb1e7c19e2f9868190284df56bcf709dbf12, relands
https://codereview.chromium.org/2266823002/.

BUG=chromium:638132
Committed: https://crrev.com/2a97b1bcb16a905ae4c10ba11f8efdfe5e2b9946
Cr-Commit-Position: refs/heads/master@{#38917}

[Jarin, 2016-08-25 13:51:30]

The CQ bit was checked by jarin@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-25 13:51:39]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[Jarin, 2016-08-25 14:03:54]

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

[Jarin, 2016-08-25 14:03:54]

Could you take a look, please?

I worked around the uninhabited type problem by using type->Is(None), which
requires both axes to be empty (so if only the representation is none, it will
still consider the value live/possible).

[commit-bot: I haz the power, 2016-08-25 14:15:26]

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

[commit-bot: I haz the power, 2016-08-25 14:15:27]

Dry run: This issue passed the CQ dry run.

[Benedikt Meurer, 2016-08-25 16:54:56]

The CQ bit was checked by bmeurer@chromium.org

[Benedikt Meurer, 2016-08-25 16:54:56]

lgtm

[commit-bot: I haz the power, 2016-08-25 16:55:07]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-08-25 16:57:40]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-08-25 16:58:24]

Description was changed from

==========
Reland of [turbofan] Insert dummy values when changing from None type.

This reverts commit a55fdb1e7c19e2f9868190284df56bcf709dbf12, relands
https://codereview.chromium.org/2266823002/.

BUG=chromium:638132
==========

to

==========
Reland of [turbofan] Insert dummy values when changing from None type.

This reverts commit a55fdb1e7c19e2f9868190284df56bcf709dbf12, relands
https://codereview.chromium.org/2266823002/.

BUG=chromium:638132

Committed: https://crrev.com/2a97b1bcb16a905ae4c10ba11f8efdfe5e2b9946
Cr-Commit-Position: refs/heads/master@{#38917}
==========

[commit-bot: I haz the power, 2016-08-25 16:58:24]

Patchset 2 (id:??) landed as
https://crrev.com/2a97b1bcb16a905ae4c10ba11f8efdfe5e2b9946
Cr-Commit-Position: refs/heads/master@{#38917}