Move the keepalive process to SipSessionImpl and make it reusable.

Reuse the new component in the original keepalive process and the NAT port
mapping timeout measurement process.

This is the foundation for fixing the following bug.

Bug: 3464181

Change-Id: If7e951c000503fa64843942ad062c4d853e20c8d
3 files changed
tree: 40a991d0ad41a3d6aaff52e17fefa445a61dca3d
  1. data/
  2. java/
  3. jni/