[XB1] Fix skipped OnDecoderDrained task.

[victorpasoshnikov]

b/284359403

[codecov]

Codecov Report

Merging #1765 (c14f287) into main (36ddc12) will decrease coverage by 0.02%.
Report is 1 commits behind head on main.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1765      +/-   ##
==========================================
- Coverage   57.77%   57.76%   -0.02%     
==========================================
  Files        1915     1915              
  Lines       95119    95119              
==========================================
- Hits        54959    54947      -12     
- Misses      40160    40172      +12     

see 4 files with indirect coverage changes

[victorpasoshnikov]

The following has place in sw (vpx, av1) decoders.
In GpuVideoDecoderBase::Reset() we have call consequence

1. decoder_thread_->job_queue()->Schedule(
   std::bind(&GpuVideoDecoderBase::DrainDecoder, this)); <- put task DrainDecoder into thread's job queue
2. decoder_thread_.reset(); <- Put task JobQueue::StopSoon and join thread
   But DrainDecoder causes OnDecoderDrained() in different thread (underlaying decoder's output thread) and the task OnDecoderDrained() can be created AFTER JobQueue::StopSoon task and can't be processed.
   To avoid this situation I had to add extra sync objects to make sure that decoder_thread_.reset() will be called after OnDecoderDrained() call

[TyHolc]

Looks good to me, I'll leave it to the media team to give a final review.

[victorpasoshnikov]

This PR must be merged together with https://lbshell-internal-review.googlesource.com/c/cobalt_src/+/267860