Add ThreadedSource to Stagefright framework

This patch adds ThreadedSource to Stagefright framework. It
allows to start Media Source in separate threads and can
significantly improve software codec (such as VP8 decoder)
performance.

Change-Id: I5fabb1e565feab8306a6ab524cd3c22b3d9976a1
Orig-Change-Id: Id1f94a1859bde7b6ff6f7a552796f75fe141e085
Signed-off-by: wfeng6 <wei.feng@intel.com>
Reviewed-on: http://android.intel.com:8080/75085
Reviewed-by: Yao, Yong <yong.yao@intel.com>
Reviewed-by: lab_cactus <lab_cactus@intel.com>
Tested-by: Tong, BoX <box.tong@intel.com>
Reviewed-by: Tong, BoX <box.tong@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>
Signed-off-by: Jian Luo <jian.luo@intel.com>
Signed-off-by: Bruce Beare <bruce.j.beare@intel.com>
Signed-off-by: Jack Ren <jack.ren@intel.com>
Author-tracking-BZ: 48043

Conflicts:

	media/libstagefright/Android.mk