Roll src/third_party/pdfium/ 78c271dd9..89f9ee3b8 (1 commit).

https://pdfium.googlesource.com/pdfium.git/+log/78c271dd9ee8..89f9ee3b8f3b

$ git log 78c271dd9..89f9ee3b8 --date=short --no-merges --format='%ad %ae %s'
2016-10-04 npm Use FX_SAFE_UINT32 on CPDF_ToUnicodeMap::Load

BUG=652232

TBR=dsinclair@chromium.org

Review-Url: https://codereview.chromium.org/2385063004
Cr-Commit-Position: refs/heads/master@{#422877}

DEPS

@@ -63,7 +63,7 @@ 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': '78c271dd9ee883f4e31e41a8adda8e615c84ad63',
+  'pdfium_revision': '89f9ee3b8f3b4756f05ff48055f4bff7353201e2',
   # 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.