This introduces a function AudioProcessingImpl::SetCreateOptionalSubmodulesForTesting to simulate the exclusion of build-optional submodules, and tests of the currently only excludable submodule. Bug: webrtc:11292 Change-Id: If492606205c9fdc669a6dce3a8989a434aeeed1f Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/173746 Commit-Queue: Sam Zackrisson <saza@webrtc.org> Reviewed-by: Per Åhgren <peah@webrtc.org> Cr-Commit-Position: refs/heads/master@{#31138}