Roll pdfium. This brings in:

8f75c67  Disable warning 4267 in pdfium until it is fixed.
e76e823  Remove unused variable orig_size.
3d07b6f  Do not disable warnings-as-errors for pdfium.

BUG=375114
R=thestig@chromium.org
TBR=thestig@chromium.org

Review URL: https://codereview.chromium.org/400483002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@283628 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": "0ce77e3c04dd17d3086adfc8781a2155fb9ceb69",
+  "pdfium_revision": "8f75c67f4e724ba44eb3d90e4033f8cc90522273",
   # 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.