Roll src/third_party/pdfium/ ad2441ef6..37b203059 (1 commit).

https://pdfium.googlesource.com/pdfium.git/+log/ad2441ef6758..37b203059210

$ git log ad2441ef6..37b203059 --date=short --no-merges --format='%ad %ae %s'
2016-10-24 weili Add ASan bots in commit queue

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/2451533002
Cr-Commit-Position: refs/heads/master@{#427231}

DEPS

@@ -63,7 +63,7 @@ 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': 'ad2441ef675866eb84c7392eeda03391a5a5d474',
+  'pdfium_revision': '37b203059210426d8739c37eb00b2ca9583fa4b6',
   # 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.