Roll PDFium from 807e4fa951b9 to 5988d0f33501 (4 revisions)

https://pdfium.googlesource.com/pdfium.git/+log/807e4fa951b9..5988d0f33501

2020-08-17 tsepez@chromium.org No need to clear local variable in XFA_LoadImageFromBuffer().
2020-08-17 tsepez@chromium.org Use fxcrt::AutoNuller<T> in CPDFXA_Context::LoadXFADoc().
2020-08-17 tsepez@chromium.org Introduce fxcrt::AutoNuller<T>.
2020-08-17 pdfium-autoroll@skia-public.iam.gserviceaccount.com Roll MarkupSafe from 8f45f5cfa000 to f2fb0f21ef1e (2 revisions)

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/pdfium-autoroll
Please CC pdfium-deps-rolls@chromium.org on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

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

Bug: None
Tbr: pdfium-deps-rolls@chromium.org
Change-Id: Ia82800de6892788482795b5de31974b1b68c63e7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2361763Reviewed-by: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Commit-Queue: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#799041}

DEPS

@@ -215,7 +215,7 @@ 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': '807e4fa951b9aae0c9355abae7d379b70a5f8677',
+  'pdfium_revision': '5988d0f33501ab96e661377f204f11b36e58276a',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling BoringSSL
   # and whatever else without interference from each other.