Roll PDFium to 8f6445b.

Roll PDFium to 8f6445b.

This pulls in a new API that allows chrome to stop including private
PDFium headers.  Chrome is modified to use it, and the inculde rules
are updated to reflect a "public header only" policy.

BUG=486818
Committed: https://crrev.com/ce5a54c7151bcbe5accb108ed81554e4bde7280d
Cr-Commit-Position: refs/heads/master@{#329487}

[Tom Sepez, 2015-05-12 19:52:26]

tsepez@chromium.org changed reviewers:
+ thestig@chromium.org

[Tom Sepez, 2015-05-12 19:52:27]

Lei, chromium side of change.  Thanks.

[Lei Zhang, 2015-05-12 20:28:41]

lgtm

[Tom Sepez, 2015-05-12 20:46:37]

The CQ bit was checked by tsepez@chromium.org

[commit-bot: I haz the power, 2015-05-12 20:49:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1129223005/1

[commit-bot: I haz the power, 2015-05-12 21:07:17]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-12 21:09:03]

Patchset 1 (id:??) landed as
https://crrev.com/ce5a54c7151bcbe5accb108ed81554e4bde7280d
Cr-Commit-Position: refs/heads/master@{#329487}