Make Clang plugin check WeakPtrFactory member order

Add Clang plugin check for WeakPtrFactory member order

Also consolidates some of the FindBadConstruct options in to a small struct for readability.

The WeakPtrFactory member order is behind a flag, because
there are many violations in Chromium right now. Also, there
might need to be exceptions in the checker. For example,
we might want to allow more than one WeakPtrFactory to refer
to the outer class, as long as all such factories appear
after all other members. That's TBD.

BUG=303818
R=erg@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=227528

[Elliot Glaysher, 2013-10-07 20:19:00]

lgtm, but please note that there's going to be a delay between now and this
going into production, since we're having some trouble rolling clang. You can
ask thakis for details, if you're interested.

[dmichael (off chromium), 2013-10-07 20:30:56]

On 2013/10/07 20:19:00, Elliot Glaysher wrote:
> lgtm, but please note that there's going to be a delay between now and this
> going into production, since we're having some trouble rolling clang. You can
> ask thakis for details, if you're interested.
Thanks, Elliot. The delay doesn't matter much; I can't turn this on by default
until I work through the ~250 violations we have. And I can use it locally in
the mean time.

[commit-bot: I haz the power, 2013-10-07 20:31:47]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/dmichael@chromium.org/26303002/9001

[commit-bot: I haz the power, 2013-10-08 01:34:05]

Retried try job too often on win_rel for step(s) browser_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_rel&nu...

[dmichael (off chromium), 2013-10-08 16:48:55]

Committed patchset #2 manually as r227528 (presubmit successful).