ImageReaderSurfaceProducer interacts poorly with (some) plugins due to ensureRunningOnMainThread #146465
Description
Some plugins may execute their Android code on another thread, i.e. not the main thread.
As a result, ImageReaderSurfaceProducer will fail at runtime, because some methods, like FlutterJNI.scheduleFrame, "must be executed on the main thread". This is blocking the migration of the camera plugin to SurfaceProducer (flutter/packages#6461). There is an example failure on Firebase Test Lab, though, sort of scarily, nowhere else (maybe this is a good candidate test for scenario_app).
Possible options:
- This check is out of date, and we could remove it (would have to be thoroughly tested)
- We need to make sure tasks are posted in the UI thread, instead of the current thread/handler