Roll src/third_party/pdfium/ 61a3cb81a..fe1c8e616 (3 commits)

https://pdfium.googlesource.com/pdfium.git/+log/61a3cb81a298..fe1c8e616680

$ git log 61a3cb81a..fe1c8e616 --date=short --no-merges --format='%ad %ae %s'
2017-07-18 reed colortables are unused, so remove plumbing
2017-07-18 rharrison Correct lexer handling of FormCalc identifiers
2017-07-18 rharrison Add tools for generating coverage information

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

Change-Id: Ibf68e8b115637a659281fdd25fd8c6c8be0987d5
Reviewed-on: https://chromium-review.googlesource.com/576190
Reviewed-by: <pdfium-deps-roller@chromium.org>
Commit-Queue: <pdfium-deps-roller@chromium.org>
Cr-Commit-Position: refs/heads/master@{#487528}

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': '61a3cb81a298640ec65fc019926a3a46b8cf8617',
+  'pdfium_revision': 'fe1c8e61668079b873922acb1e56d0ea55a3c375',
   # 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.