Roll PDFium from 0517bfe506ad to 79a76200e48b (13 revisions)

https://pdfium.googlesource.com/pdfium.git/+log/0517bfe506ad..79a76200e48b

2020-10-23 thestig@chromium.org Remove loading of unused gdiplus functions.
2020-10-23 thestig@chromium.org Remove most CFX_WindowsDIB code.
2020-10-23 tsepez@chromium.org Bicubic image transforms are not used by PDFium.
2020-10-22 thestig@chromium.org Further reduce manual memory management in CGdiplusExt::LoadDIBitmap().
2020-10-22 tsepez@chromium.org Remove some references to |cmyk| from fxge/dib.
2020-10-22 tsepez@chromium.org Make class CFX_DIBitmap::Channel private.
2020-10-22 thestig@chromium.org Replace manual memory allocation / deletion with a unique_ptr.
2020-10-22 tsepez@chromium.org Remove arguments from CFX_DIBitmap::LoadChannel()
2020-10-22 tsepez@chromium.org Make FXDIB_Channel an enum class and nest in CFX_DIBitmap.
2020-10-22 thestig@chromium.org Remove unused members in CFX_ImageStretcher.
2020-10-22 thestig@chromium.org Remove a CFX_DIBitmap::CompositeRect() parameter.
2020-10-22 thestig@chromium.org Slightly simplify CFX_ImageTransformer.
2020-10-22 thestig@chromium.org Use more spans in CFX_ScanlineCompositor for palette data.

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: Ied0c7de04ce1d0c6f4cdb9d074c1281acea901ea
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2494516Reviewed-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@{#820181}

DEPS

@@ -226,7 +226,7 @@ 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': '0517bfe506adccd4815c7927953089d81b03d353',
+  'pdfium_revision': '79a76200e48b5b439ef4f3465cea563b40af555f',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling BoringSSL
   # and whatever else without interference from each other.