Roll PDFium from 6beab305c5ad to 5fa76bf3acca (6 revisions)

https://pdfium.googlesource.com/pdfium.git/+log/6beab305c5ad..5fa76bf3acca

2021-09-03 tsepez@chromium.org Remove CXFA_FFDoc::m_pXMLDoc.
2021-09-03 tsepez@chromium.org Remove CPDF_StreamContentParser::m_pLastTextObject.
2021-09-03 tsepez@chromium.org Remove CPDF_ScaledRenderBuffer::m_pObject and m_pContext
2021-09-03 tsepez@chromium.org Simplify calls to CPVT_FontMap::GetAnnotSysPDFFont()
2021-09-03 tsepez@chromium.org Remove unused member CPDF_TransferFunc::m_pPDFDoc.
2021-09-03 tsepez@chromium.org Replace CFX_SizeF with discrete floats for ranges in CFWL_ classes.

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 file a bug in PDFium: https://bugs.chromium.org/p/pdfium/issues/entry
To file a bug in Chromium: https://bugs.chromium.org/p/chromium/issues/entry

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/main/autoroll/README.md

Bug: None
Tbr: pdfium-deps-rolls@chromium.org
Change-Id: I1f82e699c0ce0fdb09d31a5d24a35378036c5893
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3141755
Commit-Queue: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Bot-Commit: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#918334}