Reason for revert: Take three of relanding this after all internal issues have been resolved. Original issue's description: > Revert of Adding backward compatibility header (patchset #1 id:1 of https://codereview.webrtc.org/2909923002/ ) > > Reason for revert: > Breaks downstream project. > > Original issue's description: > > Adding backward compatibility header > > > > This header will be removed ad soon as downstream projects will be > > updated. > > > > BUG=webrtc:4867 > > NOTRY=True > > TBR=kjellander@webrtc.org > > > > Review-Url: https://codereview.webrtc.org/2909923002 > > Cr-Commit-Position: refs/heads/master@{#18306} > > Committed:4fa8a97cc3> > TBR=kjellander@webrtc.org,magjed@webrtc.org > # Skipping CQ checks because original CL landed less than 1 days ago. > NOPRESUBMIT=true > NOTREECHECKS=true > NOTRY=true > BUG=webrtc:4867 > > Review-Url: https://codereview.webrtc.org/2908143003 > Cr-Commit-Position: refs/heads/master@{#18308} > Committed:6684fdce93TBR=kjellander@webrtc.org,magjed@webrtc.org # Skipping CQ checks because original CL landed less than 1 days ago. NOPRESUBMIT=true NOTREECHECKS=true NOTRY=true BUG=webrtc:4867 Review-Url: https://codereview.webrtc.org/2912773003 Cr-Commit-Position: refs/heads/master@{#18320}