Roll src/third_party/pdfium/ 19cd7cc42..470b5fa8f (1 commit).

https://pdfium.googlesource.com/pdfium.git/+log/19cd7cc42700..470b5fa8f8db

$ git log 19cd7cc42..470b5fa8f --date=short --no-merges --format='%ad %ae %s'
2016-11-07 thestig Compile fuzzer sources in standalone builds.

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/2483833002
Cr-Commit-Position: refs/heads/master@{#430277}

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': '19cd7cc42700b844e6d9fc170a65bf7122d468b8',
+  'pdfium_revision': '470b5fa8f8dbfd2aa702d9d8cfdc03a7b486b374',
   # 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.