Roll src/third_party/pdfium/ 8779fa857..52ef14e89 (2 commits).

https://pdfium.googlesource.com/pdfium.git/+log/8779fa8578cf..52ef14e8911f

$ git log 8779fa857..52ef14e89 --date=short --no-merges --format='%ad %ae %s'
2016-10-12 ethannicholas added SkSL to Skia build
2016-10-12 dsinclair Convert from int to float values.

BUG=652038

TBR=dsinclair@chromium.org

Review-Url: https://codereview.chromium.org/2417653002
Cr-Commit-Position: refs/heads/master@{#424873}