Roll PDFium from 33792a19b6e2 to b6525ec96573 (8 revisions)

https://pdfium.googlesource.com/pdfium.git/+log/33792a19b6e2..b6525ec96573

2020-09-10 thestig@chromium.org Fix non-standalone XFA build.
2020-09-10 tsepez@chromium.org Nest CXFA_TextPiece and CXFA_PieceLine in CXFA_TextLayout
2020-09-09 tsepez@chromium.org Better encapsulate CFXA_TextLayout::m_pieceLines.
2020-09-09 tsepez@chromium.org Remove out paramenters from CXFA_TextLayout::GetUnderline()
2020-09-09 tsepez@chromium.org Nest CXFA_LoaderContext inside CXFA_TextLayout
2020-09-09 tsepez@chromium.org Make CXFA_FontMgr a garbage-collected class
2020-09-09 tsepez@chromium.org Make fxjs/gc be its own source_set
2020-09-09 tsepez@chromium.org No need to observe garbage-collected CXFA_FFWidget either.

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: I2b956409d4a4b64d78ce3dd8d3e904510584e403
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2402645Reviewed-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@{#805677}

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': '33792a19b6e282c7f3219420b10b6f027dc1fde2',
+  'pdfium_revision': 'b6525ec96573078b680538b7c4e12acce59d4574',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling BoringSSL
   # and whatever else without interference from each other.