DataSource: Split off ffmpeg sniffer to a second pass, and only if necessary

ffmpeg's sniffer is intended as a grab-all-that-doesn't-work-elsewhere
extractor. Unfortunately, this causes two issues:

- As written, it requires ffmpeg to whitelist any extractors supported
by stagefright, or else it will blindly override them. This has codebase
sync issues, as shown by the VP9 and WAV accidental overrides
- It imposes an in-depth analysis of _all_ media, even that which we
want to be processed quickly by shipping stagefright plugins (hardware
or not). This is mostly noticeable in network streams and thumbnail
generation.

This patch moves FFmpegExtractor to an independent sniffer queue, and
it only invokes it when the regular MediaExtractor hits 1 of 3 conditions:

1 - The confidence in the identified container type is low
2 - No container is identified at all
3 - A video container was found by other extractors, but only 1 stream
(audio or video) was identified.

Change-Id: Ib96ff4f6bc06223fe0e819a57560d3c872a79ddd
disable camera sounds (3/3)

Change-Id: Iff4eb5ca7dd13038bf852a76d0c605814864497a
Signed-off-by: Jonathan Steadman <xxwhitehawk@gmail.com>
screenrecord: Add audio support

Adds audio recording to the screenrecord system. Note that
while recording, the audio is muted from the device output,
and that the audio volume is controlled separately (so make
sure to turn up your volume if you hear nothing).
Audio from the microphone can also be recorded by adding
--microphone to the command line.

Change-Id: I97dfcaf3d93b786c5466e1f4215549e3d015bcf0
screenrecord: Enable SUBMIX_IN as well and cleanup on exit

While on Nexus 5/Nexus 7 (AOSP QCOM audio), trying to turn on
SUBMIX_IN fails and is not needed, it is required on Find 5
and N1 (CAF QCOM audio), or otherwise SUBMIX_OUT won't turn
on.
We also now release the audio routing as it wouldn't revive
the audio speakers otherwise.

Change-Id: I0f80a232304733e0b0a834b188b8cfa5b88915f3