Omnibox - Fix Rare HQP Crash

Omnibox - Fix Rare HQP Crash

In the days of yore, there was an HQP crash:
https://code.google.com/p/chromium/issues/detail?id=359270

I put a band-aid on the crash:
https://codereview.chromium.org/222783006

Later, I fixed the root cause:
https://codereview.chromium.org/255423002
Or at least I thought I did and close that days-of-yore bug.

Apparently this didn't entirely fix the problem.  (See the linked bug
below.) I do not know what kind of situation can cause this crash any
longer. (As I said, I thought I fixed the root cause.)  But it's still
appearing. I haven't been able to get anyone to help me look into the
minidumps after more than a month of hunting.  So I'll fix this crash
the same as I did before.

This change basically restores the band-aid fix from earlier.  It'll
prevent the bad information about what offsets to highlight from
crashing the browser.

It also expands on the DCHECK message in hopes that it makes it more likely
that someone files a bug upon seeing it.

BUG=464926

[Mark P, 2015-05-11 21:19:41]

mpearson@chromium.org changed reviewers:
+ pkasting@chromium.org

[Mark P, 2015-05-11 21:20:56]

Please take a look, thanks.

[Peter Kasting, 2015-05-11 22:09:00]

If you need to figure out when something bad is happening, change the DCHECK to
a CHECK and use something like the facilities in crash_logging.h to add the
information you need to the crash dump so you can collect enough info to fix
things properly.

[Mark P, 2015-05-13 20:07:46]

I'm abandoning this patch in favor of
https://codereview.chromium.org/1133533003/

--mark