Added paused state to NuPlayerDecoder

This prevents decoder from requesting new buffer until the decoder
is resumed, and prevents processing a potential DISCONTINUITY while
the player is still flushing.

Bug: 13133027

Change-Id: I2f9fa9f00c8583aa6908809cb7c31ddde07cfaf0
(cherry picked from commit 704e72658b1082264a26a83c50046da34f07d1a1)
2 files changed