Roll src/third_party/pdfium/ 04a407093..d0bbccdd3 (1 commit).

https://pdfium.googlesource.com/pdfium.git/+log/04a407093c13..d0bbccdd3211

$ git log 04a407093..d0bbccdd3 --date=short --no-merges --format='%ad %ae %s'
2016-12-28 tsepez Make CFX_Observable copy constructable.

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/2605913003
Cr-Commit-Position: refs/heads/master@{#440888}

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': '04a407093c135cdf08644a03c210ae2182869254',
+  'pdfium_revision': 'd0bbccdd32113baf95ae16565c0314166d989638',
   # 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.