Roll src/third_party/pdfium/ 61f8e9c5a..50feafc7f (1 commit).

https://pdfium.googlesource.com/pdfium.git/+log/61f8e9c5aeb0..50feafc7f367

$ git log 61f8e9c5a..50feafc7f --date=short --no-merges --format='%ad %ae %s'
2016-11-09 thestig Roll DEPS for clang to 63ca7c81.

BUG=663913

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/2488833006
Cr-Commit-Position: refs/heads/master@{#431212}

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': '61f8e9c5aeb0d8cb5477e0248b685214746bada7',
+  'pdfium_revision': '50feafc7f367a87b7e4e689421eb7ae1484660d9',
   # 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.