On some devices, pausing+resuming (or seeking) would restart playback
from the beginning, but show a progress bar further up. This seems to
have been caused by same race condition-y thing where we were seeking
multiple times in rapid succession. Now we'll only play once, and things
seem to be fine now.
Also removed usage of some deprecated methods.
Fixes#8432
There are several (popular) phone models out there that have bugs in
their MediaPlayer implementation that cause them to be unable to play
voice notes. By moving to ExoPlayer, an application-level media player,
we should avoid most of these headaches and stardardize playback.
Fixes#7748
1) Remove all our PDU code and switch to the PDU code from the
klinker library
2) Switch to using the system Lollipop MMS library by default,
and falling back to our own custom library if that fails.
3) Format SMIL differently, using code from klinker instead of
what we've pieced together.
4) Pull per-carrier MMS media constraints from the XML config
files in the klinker library, instead of hardcoding it at 280kb.
Hopefully this is an improvement, but given that MMS is involved,
it will probably make things worse instead.
