Memory leak in HlsMediaChunk
Hello.
We have m3u8 file format such as:
```

#EXTM3U
#EXT-X-STREAM-INF:BANDWIDTH=490000,RESOLUTION=640x360
http://XXX.XXX.XX.XXX:31213/MEDIA/76336503.....583609776254/161/4161/
#EXT-X-STREAM-INF:BANDWIDTH=1500000,RESOLUTION=720x576
http://XXX.XXX.XX.XXX:31213/MEDIA/76336503.....583609776254/161/3161/
#EXT-X-STREAM-INF:BANDWIDTH=2500000,RESOLUTION=1280x720
http://XXX.XXX.XX.XXX:31213/MEDIA/76336503.....583609776254/161/2161/

```
Each EXT-X-STREAM-INF tag link to file like:
```
#EXTM3U
#EXT-X-TARGETDURATION:5
#EXT-X-VERSION:3
#EXT-X-MEDIA-SEQUENCE:35156
#EXT-X-START:TIME-OFFSET=-25,PRECISE=YES
#EXT-X-KEY:METHOD=AES-128,URI="http://XXX.XXX.XX.XXX:02444/xxXXXXX/XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/191/2191/aeskey_191_
#EXTINF:5,
http://XXX.XXX.XX.XXX:XXXXX/SSEGMENT/3020314583628416652818934133893/191/2191/seg_XXXXX.ts
#EXTINF:5,
http://XXX.XXX.XX.XXX:XXXXX/SSEGMENT/6545456465456456465454564/191/2191/seg_191_XXXXX.ts
#EXTINF:5,
http://XXX.XXX.XX.XXX:XXXXX/SSEGMENT/6545456465456456465454564/191/2191/seg_191_XXXXX.ts
#EXTINF:5,
http://XXX.XXX.XX.XXX:XXXXX/SSEGMENT/6545456465456456465454564/191/2191/seg_191_XXXXX.ts
#EXTINF:5,
http://XXX.XXX.XX.XXX:XXXXX/SSEGMENT/6545456465456456465454564/191/2191/seg_191_XXXXX.ts
```
Large heap set to true.
After 2-3 hours of playing we have this video freeze and log is - [Log2.zip](https://github.com/google/ExoPlayer/files/701610/Log2.zip)

If we set large heap to false, then video freezes much faster and then we have out of memory exception.
