Roll src/third_party/pdfium/ fbecb9a51..e06880f8e (2 commits)

https://pdfium.googlesource.com/pdfium.git/+log/fbecb9a5150d..e06880f8eb98

$ git log fbecb9a51..e06880f8e --date=short --no-merges --format='%ad %ae %s'
2018-04-18 thestig Fix integer overflow in shading drawing code.
2018-04-18 tsepez Always build JS Runtime stubs even if V8 present.

Created with:
  roll-dep src/third_party/pdfium
BUG=chromium:833721


The AutoRoll server is located here: https://pdfium-roll.skia.org

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff, who should
be CC'd on the roll, and stop the roller if necessary.


TBR=dsinclair@chromium.org

Change-Id: I5f24866aeca19c08d4e8f0459180c5b617263dc6
Reviewed-on: https://chromium-review.googlesource.com/1018119
Reviewed-by: pdfium-chromium-autoroll <pdfium-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Commit-Queue: pdfium-chromium-autoroll <pdfium-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#551912}