Update PDFium to 1b24b69.

Update PDFium to 1b24b69.

The only change since the previous revision is unconditionally using
static_assert in third_party/macros.h.  This gets rid of the old code that used
ALLOW_UNUSED and will ensure there are no conflicts of any kind as I change how
the version of ALLOW_UNUSED in Chromium works.

BUG=81439
TEST=none
TBR=jam

Committed: https://crrev.com/6820c70743002d71f11c28c99602a76d989b70b1
Cr-Commit-Position: refs/heads/master@{#299412}

[Peter Kasting, 2014-10-14 00:01:49]

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

[Peter Kasting, 2014-10-14 00:02:25]

TBRing jam for this change since he reviewed it when it landed upstream a few
weeks ago.

[Peter Kasting, 2014-10-14 00:02:28]

The CQ bit was checked by pkasting@chromium.org

[commit-bot: I haz the power, 2014-10-14 00:03:49]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/654783003/1

[commit-bot: I haz the power, 2014-10-14 01:14:06]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-10-14 01:14:52]

Patchset 1 (id:??) landed as
https://crrev.com/6820c70743002d71f11c28c99602a76d989b70b1
Cr-Commit-Position: refs/heads/master@{#299412}