Requesting a cherry-pick of this fix to stable (3.44) — and, since the
current 3.46 candidate branch appears to have been cut before this merge,
possibly beta as well. Per the cherry-pick process, providing the required
fields below in the hope a team member can apply the cp: label(s).

Impacted Users: Any app rendering sustained SurfaceProducer-backed
textures on Android 13+ — this includes the stock video_player plugin
(video_player_android 2.9.5), not only flutter_webrtc. End customers of
3.44-built apps.

Impact Description: One sync_file fd leaks per rendered frame; the process
hits the 32768 RLIMIT_NOFILE ceiling mid-session. Fence dup/merge then fails
with EMFILE, the raster thread blocks forever in Surface::dequeueBuffer, and
the app freezes permanently (silent freeze, or "Input dispatching timed out"
ANR in flutter::SurfaceChanged if the user touches the screen).

Production data from our fitness app (30-60 min workout sessions with looping
exercise videos + animated WebP thumbnails):

• Fleet version bisect: zero "Too many open files" events across 90 days
  of Flutter 3.41.x-built releases (~15 versions); first EMFILE event 2
  days after our first 3.44.1-built release. Our Play user-perceived ANR
  rate was pushed above the 0.47% "bad behavior" threshold primarily by this
  cluster.
• We downgraded production to 3.41.9 as mitigation, but even there the leak
  exists and is only masked by GC reclaim (as noted in [Android] ImageReaderSurfaceProducer.waitOnFence leaks one sync_file FD per frame (image.getFence() never closed) → freeze at FD limit (API 33+) #188161): our fd
  telemetry shows sessions stalling at openFileDescriptors=32759.

Workaround: None in-app; the leak is in the engine's Java embedding. We
downgraded to 3.41.x and disabled animated thumbnails on Android.

Risk: Low — the fix closes an AutoCloseable (SyncFence) immediately
after awaitForever() via try-with-resources; small, local, merged on master
since 2026-06-24, with a regression test asserting close() is called.

Test Coverage: Reproduction in #188161 (flutter_webrtc example, Pixel 6a);
regression test in this PR.

Validation Steps: Run any long video_player session on an Android 13+
device and watch ls /proc/<pid>/fd | wc -l — flat with the fix, climbs
per-frame without it. We additionally ship fd-count telemetry in production
and can verify a hotfix build against a fleet that reproduces this weekly.