lavc/pngdec: restructure exporting frame meta/side data

This data cannot be stored in PNGDecContext.picture, because the
corresponding chunks may be read after the call to
ff_thread_finish_setup(), at which point modifying shared context data
is a race.

Store intermediate state in the context and then write it directly to
the output frame.

Fixes exporting frame metadata after 5663301560
Fixes #8972

Found-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
(cherry picked from commit 8d74baccff59192d395735036cd40a131a140391)
Signed-off-by: Anton Khirnov <anton@khirnov.net>

0 files changed, 0 insertions, 0 deletions