Roll src/third_party/pdfium/ 67ccef73b..40870db0a (6 commits)

https://pdfium.googlesource.com/pdfium.git/+log/67ccef73bf66..40870db0aade

$ git log 67ccef73b..40870db0a --date=short --no-merges --format='%ad %ae %s'
2017-07-19 drgage Add FPDFAnnot_GetFormFieldAtPoint() and embedder tests.
2017-07-19 drgage Add FPDFAnnot_GetFormFieldFlags() and associated embedder tests.
2017-07-19 tsepez Rename StringCs c_str() to unterminated_c_str().
2017-07-19 caryclark fix continue skia cache flush
2017-07-19 dsinclair Remove unused GetThisAppearanceStream
2017-07-19 dsinclair Create CPWL_AppStream.

Created with:
  roll-dep src/third_party/pdfium
BUG=59266,59266


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: If4c2a89080c44d782e6ae44431cfd20c33b2ffff
Reviewed-on: https://chromium-review.googlesource.com/578678
Reviewed-by: <pdfium-deps-roller@chromium.org>
Commit-Queue: <pdfium-deps-roller@chromium.org>
Cr-Commit-Position: refs/heads/master@{#488137}

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': '67ccef73bf664b7cdb4c6eed7acbaa4163c22a80',
+  'pdfium_revision': '40870db0aadef4e145fd3b2b95fa5a083afb3161',
   # 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.