Roll src/third_party/pdfium/ 04d792fb7..507fb4ed0 (3 commits)

https://pdfium.googlesource.com/pdfium.git/+log/04d792fb7510..507fb4ed09d5

$ git log 04d792fb7..507fb4ed0 --date=short --no-merges --format='%ad %ae %s'
2018-03-08 dsinclair Convert Before{Selection|Value}Change to return a bool
2018-03-08 dsinclair Remove BeforeFormImportData and BeforeFormReset
2018-03-08 dsinclair Remove uncalled AfterFormImportData

Created with:
  roll-dep src/third_party/pdfium


The AutoRoll server is located here: https://pdfium-roll.skia.org

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff, who should
be CC'd on the roll, and stop the roller if necessary.


TBR=dsinclair@chromium.org

Change-Id: I5d32f2d2e118b6cc7b63341f9e8d3670e238dc2e
Reviewed-on: https://chromium-review.googlesource.com/955776
Commit-Queue: pdfium-chromium-autoroll <pdfium-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Reviewed-by: pdfium-chromium-autoroll <pdfium-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#541867}

DEPS

@@ -103,7 +103,7 @@ 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': '04d792fb7510e328f508bc81379ca15791af93e7',
+  'pdfium_revision': '507fb4ed09d5fbc92fafdfe405d79d44d11a4664',
   # 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.