Roll src/third_party/pdfium/ 4bed2af0c..f6ee82073 (2 commits).

https://pdfium.googlesource.com/pdfium.git/+log/4bed2af0c049..f6ee820732b8

$ git log 4bed2af0c..f6ee82073 --date=short --no-merges --format='%ad %ae %s'
2016-12-05 jbudorick [android] Make pdfium_unittests work on Android.
2016-12-05 caryclark enable skia gradients, fix bugs

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

If the roll is causing failures, see:
http://www.chromium.org/developers/tree-sheriffs/sheriff-details-chromium#TOC-Failures-due-to-DEPS-rolls

TBR=dsinclair@chromium.org

Review-Url: https://codereview.chromium.org/2549143002
Cr-Commit-Position: refs/heads/master@{#436318}

DEPS

@@ -64,7 +64,7 @@ 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': '4bed2af0c049bf499dcdb1327a47d40b4c0db92d',
+  'pdfium_revision': 'f6ee820732b8717d32d85a47938172080067ce4e',
   # 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.