Reason for revert: Break downstream tests. Original issue's description: > Allow custom metrics implementations on Android. > > BUG=webrtc:6499 > > Committed: https://crrev.com/de609b26c5fc77fd3388eae5594ee8a634edf8da > Cr-Commit-Position: refs/heads/master@{#15169} TBR=kjellander@webrtc.org,magjed@webrtc.org,sakal@webrtc.org # Skipping CQ checks because original CL landed less than 1 days ago. NOPRESUBMIT=true NOTREECHECKS=true NOTRY=true BUG=webrtc:6499 Review-Url: https://codereview.webrtc.org/2516403002 Cr-Commit-Position: refs/heads/master@{#15171}