sceAvPlayerAddSource queues an auto start for a player created with auto
start or without an event callback. When the title enabled its streams
and called sceAvPlayerStart before the controller thread ran it, the auto
start called Start again on the playing player, which stopped it, released
every video buffer, including the frame the title held, and started the
film over. guest_avplayer occasionally caught this as "video frame is not
a texture allocation"; right after the test's own start, 8 texture
buffers were released in 15 of 15 runs.
The auto start now starts the player only while it is still ready, and
checks that under the player lock together with the start.
TestAutoStartKeepsStartedPlayback starts a callback-less player itself and
checks that no texture buffer is released afterwards and that the frame
it holds stays allocated. It fails on every run without the fix.
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