This also fixes an overflow bug when calculating the presentation
timestamp by making input_fragment_index_ a 64-bit int.

Test: manually check that playback works
Bug: 146030443

Change-Id: Ied31c00fcab11d1af35195c4848fe9557b5bee3a
(cherry picked from commit beaff8e102e0f57e35cb11add86f5270f045fbae)