Roll src/third_party/pdfium/ 72a22025e..47fb8c06a (7 commits).

https://pdfium.googlesource.com/pdfium.git/+log/72a22025ec44..47fb8c06acd0

$ git log 72a22025e..47fb8c06a --date=short --no-merges --format='%ad %ae %s'
2016-12-15 tsepez Return unique_ptr from CFX_BinaryBuf::DetachBuffer()
2016-12-15 dsinclair Move window type mask up with masked flags
2016-12-15 dsinclair Remove widget offscreen code.
2016-12-15 dsinclair Cleanup widget edge related code
2016-12-15 dsinclair Remove more unused widget styles
2016-12-15 dsinclair Remove unused widget state flags
2016-12-15 dsinclair Remove unused sysbtn code

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/2577283002
Cr-Commit-Position: refs/heads/master@{#439013}

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': '72a22025ec4402178cd0b27239bf77cf3a953949',
+  'pdfium_revision': '47fb8c06acd0ff9ea50c8c2d7f67510ea5c28577',
   # 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.