Revert of Remove DCHECK_IMPLIES/CHECK_IMPLIES.

Revert of Remove DCHECK_IMPLIES/CHECK_IMPLIES. (patchset #3 id:40001 of https://codereview.chromium.org/1421483005/ )

Reason for revert:
breaks compilation on multiple builders, including but not limited to:

http://build.chromium.org/p/chromium.webkit/builders/WebKit%20Mac%20Builder%20%28dbg%29/builds/132580
http://build.chromium.org/p/chromium.linux/builders/Android%20Builder%20%28dbg%29/builds/91670

Original issue's description:
> Remove DCHECK_IMPLIES/CHECK_IMPLIES.
>
> This patch removes both DCHECK_IMPLIES and CHECK_IMPLIES macros.
>
> R=thakis, sky, jam
> CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel
>
> Committed: https://crrev.com/cc8936ba36ee29b5859f65c936e16f87eeac82b4
> Cr-Commit-Position: refs/heads/master@{#356193}

TBR=thakis@chromium.org,sky@chromium.org,jam@chromium.org,vmpstr@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Committed: https://crrev.com/625f6c8cd6bda5cd7a5b1691376956bb8f300785
Cr-Commit-Position: refs/heads/master@{#356202}

[jbudorick, 2015-10-27 00:52:45]

Created Revert of Remove DCHECK_IMPLIES/CHECK_IMPLIES.

[commit-bot: I haz the power, 2015-10-27 00:53:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1417903005/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1417903005/1

[commit-bot: I haz the power, 2015-10-27 00:55:00]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-27 00:56:03]

Patchset 1 (id:??) landed as
https://crrev.com/625f6c8cd6bda5cd7a5b1691376956bb8f300785
Cr-Commit-Position: refs/heads/master@{#356202}