Work around a parameter-unused-but-set warning in gin/

Work around a parameter-unused-but-set warning in gin/

GCC thinks that the create_flags parameter in the templated class
gin::Invoker constructor is going unused, even though it is definitely
being used as a part of a variadic template expansion. Convince GCC
that it is in fact being used by casting it to a void.

BUG=424334
TEST=Linux GN build of gin with is_clang=false
R=aa

Committed: https://crrev.com/a34136a3c2eeefab5e700633e317ecb1428602de
Cr-Commit-Position: refs/heads/master@{#302361}

[Chris Masone, 2014-10-31 21:47:19]

cmasone@chromium.org changed reviewers:
+ aa@chromium.org, jyasskin@chromium.org
- aa@google.com

[Aaron Boodman, 2014-10-31 22:11:30]

lgtm

[Chris Masone, 2014-10-31 23:12:02]

The CQ bit was checked by cmasone@chromium.org

[commit-bot: I haz the power, 2014-10-31 23:13:22]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/694063002/1

[commit-bot: I haz the power, 2014-11-01 00:10:55]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-11-01 00:11:55]

Patchset 1 (id:??) landed as
https://crrev.com/a34136a3c2eeefab5e700633e317ecb1428602de
Cr-Commit-Position: refs/heads/master@{#302361}