Add a crash-hunting CHECK() in RenderProcessHostImpl::AddRoute()

Add a crash-hunting CHECK() in RenderProcessHostImpl::AddRoute()

This is an equivalent of DCHECK() in IDMap.
According to crbug.com/381990, this can occasionally crash.
I'd like to enable this to collect more data if it still crashes.
If you see this CHECK() being hit in the wild,
please revert this change and let me know.

BUG=381990, 415059
R=nasko@chromium.org, amineer@chromium.org

Committed: https://crrev.com/9a8e3d71f73ace82874d53ba2e749b1173a98513
Cr-Commit-Position: refs/heads/master@{#299146}

[nasko, 2014-10-10 02:45:31]

lgtm

[Hajime Morrita, 2014-10-10 17:56:49]

The CQ bit was checked by morrita@chromium.org

[commit-bot: I haz the power, 2014-10-10 17:58:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/647623003/1

[amineer_google, 2014-10-10 18:11:29]

amineer@google.com changed reviewers:
+ karen@chromium.org

[amineer_google, 2014-10-10 18:11:55]

On 2014/10/10 17:58:23, I haz the power (commit-bot) wrote:
> CQ is trying da patch. Follow status at
>  https://chromium-cq-status.appspot.com/patch-status/647623003/1

+karen (who owns M40 for desktop and thus needs to know about this).

[commit-bot: I haz the power, 2014-10-10 18:30:10]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-10-10 18:31:02]

Patchset 1 (id:??) landed as
https://crrev.com/9a8e3d71f73ace82874d53ba2e749b1173a98513
Cr-Commit-Position: refs/heads/master@{#299146}

[kareng, 2014-10-11 19:30:17]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/645233003/ by kareng@google.com.

The reason for reverting is: per bug
https://code.google.com/p/chromium/issues/detail?id=422694 a bunch of crashes
both in mac and windows today's canary..