stagefright: Handle missing text track language

Only set timed text language if kKeyMediaLanguage is found.

Crs-Fixed: 641896

Change-Id: Ie471bc458e42f5728064e447ac5c33b07311d3fd
Fix kAutoRampDurationUs overflow issue

When kAutoRampDurationUs multiplies with mSampleRate, it overflows to int64.
Type cast it to int64 to make sure RampDurationUs properly.

BUg: 11162491
Change-Id: I4f93bc9acc8456e25623a9255ca7a5b206425009
audio: calculate mute duration using getOutputLatency

-AudioSource mutes for predefined duration
 (kAutoRampStartUs)  at the beginning of a recording.
 Since kAutoRampStartUs is zero, video recording tone
 is also getting recorded in the beggining.

-Fix is to get the output latency of current playback
 stream from audio system to calculate mute duration.

Change-Id: Ib9f4d38fcc8478d148719b70358644c581ba2f25
CRs-fixed: 615511