Roll src/third_party/pdfium/ 52c73c24a..5c1961dfa (1 commit)

https://pdfium.googlesource.com/pdfium.git/+log/52c73c24ab05..5c1961dfa0b1

$ git log 52c73c24a..5c1961dfa --date=short --no-merges --format='%ad %ae %s'
2017-03-10 npm Add public method FPDFText_GetTextIndexFromCharIndex

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

Review-Url: https://codereview.chromium.org/2740013006
Cr-Commit-Position: refs/heads/master@{#456157}

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': '52c73c24ab053e839182d3cdac6cbb758ce3a196',
+  'pdfium_revision': '5c1961dfa0b1828eb2db38dc637548584c5cc704',
   # 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.