Roll pdfium. Things brings in:

22b31e0  Adjust null object check
baca770  Fix remaining -Wdelete-non-virtual-dtor violations on Windows.

BUG=none
R=thestig@chromium.org
TBR=thestig

Review URL: https://codereview.chromium.org/410513003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284579 0039d316-1c4b-4281-b951-d872f2087c98

DEPS

@@ -77,7 +77,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling PDFIum
   # and whatever else without interference from each other.
-  "pdfium_revision": "b72977f8c3efda2ceea6d25b1e042dfd6ea49c77",
+  "pdfium_revision": "22b31e0b3d14a50c4dd70ed22e0f24975dc1137c",
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling openmax_dl
   # and whatever else without interference from each other.