Roll src/third_party/pdfium/ f768baf12..185312303 (1 commit)

https://pdfium.googlesource.com/pdfium.git/+log/f768baf129fc..185312303814

$ git log f768baf12..185312303 --date=short --no-merges --format='%ad %ae %s'
2017-07-14 npm Simplify CJBig2_Context::huffman_assign_code

Created with:
  roll-dep src/third_party/pdfium


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

Change-Id: Ifce70100befc5ba275a7347dfb2fa84ec2b8d0a4
Reviewed-on: https://chromium-review.googlesource.com/574671
Reviewed-by: <pdfium-deps-roller@chromium.org>
Commit-Queue: <pdfium-deps-roller@chromium.org>
Cr-Commit-Position: refs/heads/master@{#487127}

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': 'f768baf129fcafc4342193477e0c41c082ef5ca5',
+  'pdfium_revision': '18531230381465592e1a037e6dfc39d4a6fb5def',
   # 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.