[Mac] Replace most uses of HAVE(MT_PLUGIN_FORMAT_READER) with ENABLE(WEBM_FORMAT_READER)
Created attachment 417107 [details] Patch
<rdar://problem/72600426>
Created attachment 417118 [details] Patch
Committed r271214: <https://trac.webkit.org/changeset/271214> All reviewed patches have been landed. Closing bug and clearing flags on attachment 417118 [details].