Remove unused member functions in audio_device_mac.h, which would cause compiling warning with clang -Wthread-safety-anaysis. Reported and fixed by mozilla. Imported here(We don't have any problem since we suppressed those warning in r7961).
Remove unused member functions in audio_device_mac.h, which would cause compiling warning with clang -Wthread-safety-anaysis. Reported and fixed by mozilla. Imported here(We don't have any problem since we suppressed those warning in r7961).

BUG=4362
TEST=AutoTest
R=henrika@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/41209004

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#8681}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 5c72922c75990f1cf0682408487fbf56078902ee

sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc