a44e72c44f
This makes it clearer that the C++ SurfaceTextureHelper owns its associated java object it. In addition, arrange so that the SurfaceTextureHelper.stopListening method (in java) can be called from any thread. BUG= Review-Url: https://codereview.webrtc.org/1988043002 Cr-Commit-Position: refs/heads/master@{#12941}