Stagefright: update decoding times for recording with batch-input

(forward-port to CM14)

One buffer from CameraSource contains mutiple input frames
in batch-mode. Output, on the other hand, is generated for
each individual buffer. This will create an imbalance in
the timestamp queue maintained to calculate ctts offsets.
Hence, parse the batch and add individual frame-timestamps
to the decoding times list.

CRs-Fixed: 793989
Change-Id: I8244198db569c2b68fd6fb6c7fb1affbeaa701ff