This CL includes the following changes: - APM runtime setting (ID + float payload) and unit tests - Swap queue of APM runtime settings used in AudioProcessingImpl - runtime settings handler that forwards the settings to APM sub-modules when a message is retrieved from the queue - Unit test placeholder to check that the pre-gain update message is correctly delivered Bug: webrtc:9138 Change-Id: Id22704af15fde2b87a4431f5ce64ad1aeafc5280 Reviewed-on: https://webrtc-review.googlesource.com/69320 Reviewed-by: Per Åhgren <peah@webrtc.org> Reviewed-by: Alex Loiko <aleloi@webrtc.org> Commit-Queue: Alessio Bazzica <alessiob@webrtc.org> Cr-Commit-Position: refs/heads/master@{#22873}