Moved timing related logic into its own function in webrtc::PayloadRouter.
Moved timing related logic into its own function in webrtc::PayloadRouter.

Bug: none
Change-Id: I4eae7a555132654dc2d0747e7d3a7ff523523058
Reviewed-on: https://webrtc-review.googlesource.com/81242
Commit-Queue: Philip Eliasson <729b5e2dca9359bca8c81d600ef9d3e554586ac9@webrtc.org>
Reviewed-by: Niels Moller <0057859e47d61d90529d0f66d9ef692cefedb46a@webrtc.org>
Reviewed-by: Stefan Holmer <eb0877843acc39f8ef6f7269937dee931c372d23@webrtc.org>
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#23593}
ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc