02bafc6379
Permits CHECKing/DCHECKing that methods are being accessed in a thread-safe manner, even if they are not used by one single thread (thread pools such as VideoToolbox OK). BUG= R=danilchap@webrtc.org, tommi@webrtc.org Review URL: https://codereview.webrtc.org/2097403002 . Cr-Commit-Position: refs/heads/master@{#13358}