[PATCH 0/1] MR4828: mf: Only preroll when starting from stopped state.

[Yuxuan Shui (＠yshui)]

Stream sink such as evr can't be prerolled a second time, and when we are
restarting from a paused state, those stream sink will already be prerolled
so don't preroll them again. Otherwise we will be waiting for Prerolled
events that will never come.

Split from !4545, splitting the fix from the tests because turns out the tests are contentious.