Roll src/third_party/pdfium/ 98c6c15ab..958e57cbe (1 commit).

https://pdfium.googlesource.com/pdfium.git/+log/98c6c15abfec..958e57cbe864

$ git log 98c6c15ab..958e57cbe --date=short --no-merges --format='%ad %ae %s'
2016-10-04 kcwu Fix cmdStageAllocMatrix parameter swap

BUG=651849

TBR=dsinclair@chromium.org

Review-Url: https://codereview.chromium.org/2396753002
Cr-Commit-Position: refs/heads/master@{#423073}