Revert of Revert of [Base] Use variadic template in callback_list.h (wave 1)

Revert of Revert of [Base] Use variadic template in callback_list.h (wave 1) (patchset #1 id:1 of https://codereview.chromium.org/663083005/)

Reason for revert:
We now don't support building with MSVC Express any more. Do shout if this change causes problems for your compiler, though.

This is part of http://crbug.com/433164

Original issue's description:
> Revert of [Base] Use variadic template in callback_list.h (wave 1) (patchset #1 id:1 of https://codereview.chromium.org/618573002/)
>
> Reason for revert:
> Breaking compilation on windows with MSVC Express.
>
> Original issue's description:
> > [Base] Use variadic template in callback_list.h
> >
> > Replace pump.py generated base/callback_list.h with variadic template version.
> >
> > BUG=None
> >
> > Committed: https://crrev.com/a28756fae426023c53542f08c1bf80397a28f677
> > Cr-Commit-Position: refs/heads/master@{#298529}
>
> TBR=ajwong@chromium.org,tzik@chromium.org
> NOTREECHECKS=true
> NOTRY=true
> BUG=None
>
> Committed: https://crrev.com/69e698364a0a82a806fc5a4994c5f2040d1ff083
> Cr-Commit-Position: refs/heads/master@{#300487}

TBR=ajwong@chromium.org,tzik@chromium.org,lfg@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=None

Committed: https://crrev.com/6117a47171092ae0e2cb00719db4e6f9395142a5
Cr-Commit-Position: refs/heads/master@{#304952}

[Nico, 2014-11-20 01:13:15]

Created Revert of Revert of [Base] Use variadic template in callback_list.h
(wave 1)

[commit-bot: I haz the power, 2014-11-20 01:14:37]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/744503002/1

[commit-bot: I haz the power, 2014-11-20 01:15:21]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-11-20 01:17:17]

Patchset 1 (id:??) landed as
https://crrev.com/6117a47171092ae0e2cb00719db4e6f9395142a5
Cr-Commit-Position: refs/heads/master@{#304952}