Make some DecisionLogic functions virtual.
Make some DecisionLogic functions virtual.

Bug: webrtc:11005
Change-Id: I86d1eadc85162abf77010d97917e5ab20f644d66
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/158783
Commit-Queue: Ivo Creusen <ab68de427b265c46935558af10238a1ba5449aeb@webrtc.org>
Reviewed-by: Sam Zackrisson <b1a93beadfe1d2f7f0106ee02b6ffcdc950aa103@webrtc.org>
Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#29684}

TimothyGu/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc,TimothyGu/libilbc,ShiftMediaProject/libilbc