In #9243 we added some thread_checker. But it shouldn't be added into PlayoutDevices() and RecordingDevices(), since these two will be invoked from RecThread and PlayoutThread too, other than the main thread.
BUG=webrtc:4852
TEST=voe_cmd_test
R=henrika@webrtc.org
Review URL: https://codereview.webrtc.org/1249573002 .
Cr-Commit-Position: refs/heads/master@{#9605}