Don't prevent extensions on Fiber if using bad Map polyfill (#9572)
Don't prevent extensions on Fiber if using bad Map polyfill (#9572)

Many Map polyfills work by adding an extra field to the key type.

In the future, we'll likely print a warning.
wmydz1/react,rricard/react,mjackson/react,prometheansacrifice/react,yangshun/react,camsong/react,yungsters/react,kaushik94/react,terminatorheart/react,tomocchino/react,chicoxyzzy/react,roth1002/react,billfeller/react,jdlehman/react,glenjamin/react,mosoft521/react,mosoft521/react,edvinerikson/react,syranide/react,maxschmeling/react,ericyang321/react,prometheansacrifice/react,rricard/react,mhhegazy/react,cpojer/react,wmydz1/react,chenglou/react,facebook/react,jquense/react,tomocchino/react,apaatsio/react,terminatorheart/react,anushreesubramani/react,edvinerikson/react,mhhegazy/react,empyrical/react,trueadm/react,empyrical/react,aickin/react,yungsters/react,camsong/react,brigand/react,krasimir/react,yangshun/react,maxschmeling/react,billfeller/react,jameszhan/react,jorrit/react,kaushik94/react,brigand/react,kaushik94/react,chenglou/react,jorrit/react,trueadm/react,Simek/react,roth1002/react,STRML/react,dilidili/react,kaushik94/react,jordanpapaleo/react,jameszhan/react,joecritch/react,maxschmeling/react,rickbeerendonk/react,terminatorheart/react,mjackson/react,jquense/react,jameszhan/react,jdlehman/react,TheBlasfem/react,jordanpapaleo/react,camsong/react,yangshun/react,krasimir/react,anushreesubramani/react,silvestrijonathan/react,flarnie/react,yiminghe/react,dilidili/react,glenjamin/react,aickin/react,jameszhan/react,anushreesubramani/react,glenjamin/react,brigand/react,tomocchino/react,mosoft521/react,jquense/react,quip/react,tomocchino/react,acdlite/react,mosoft521/react,nhunzaker/react,ericyang321/react,silvestrijonathan/react,acdlite/react,empyrical/react,mhhegazy/react,tomocchino/react,quip/react,rricard/react,mjackson/react,edvinerikson/react,anushreesubramani/react,VioletLife/react,jdlehman/react,tomocchino/react,jordanpapaleo/react,yangshun/react,chenglou/react,jorrit/react,edvinerikson/react,aickin/react,jorrit/react,billfeller/react,kaushik94/react,joecritch/react,rricard/react,tomocchino/react,silvestrijonathan/react,billfeller/react,VioletLife/react,STRML/react,yangshun/react,kaushik94/react,rickbeerendonk/react,joecritch/react,VioletLife/react,dilidili/react,pyitphyoaung/react,brigand/react,glenjamin/react,quip/react,TheBlasfem/react,syranide/react,flarnie/react,yungsters/react,dilidili/react,yiminghe/react,camsong/react,jdlehman/react,TheBlasfem/react,STRML/react,chicoxyzzy/react,billfeller/react,AlmeroSteyn/react,flarnie/react,pyitphyoaung/react,jameszhan/react,dilidili/react,acdlite/react,jordanpapaleo/react,nhunzaker/react,acdlite/react,jdlehman/react,flarnie/react,chicoxyzzy/react,silvestrijonathan/react,trueadm/react,apaatsio/react,billfeller/react,STRML/react,joecritch/react,nhunzaker/react,brigand/react,jameszhan/react,ArunTesco/react,brigand/react,terminatorheart/react,AlmeroSteyn/react,kaushik94/react,STRML/react,jquense/react,chicoxyzzy/react,chicoxyzzy/react,empyrical/react,rricard/react,chenglou/react,jzmq/react,AlmeroSteyn/react,silvestrijonathan/react,camsong/react,trueadm/react,jquense/react,yiminghe/react,acdlite/react,rickbeerendonk/react,mjackson/react,terminatorheart/react,STRML/react,krasimir/react,pyitphyoaung/react,trueadm/react,prometheansacrifice/react,yiminghe/react,empyrical/react,VioletLife/react,syranide/react,Simek/react,jzmq/react,glenjamin/react,krasimir/react,facebook/react,yiminghe/react,jzmq/react,anushreesubramani/react,dilidili/react,Simek/react,mhhegazy/react,edvinerikson/react,Simek/react,pyitphyoaung/react,facebook/react,jorrit/react,ArunTesco/react,Simek/react,mjackson/react,rickbeerendonk/react,edvinerikson/react,cpojer/react,joecritch/react,terminatorheart/react,apaatsio/react,pyitphyoaung/react,roth1002/react,anushreesubramani/react,facebook/react,jzmq/react,mjackson/react,jquense/react,TheBlasfem/react,leexiaosi/react,cpojer/react,mjackson/react,AlmeroSteyn/react,silvestrijonathan/react,chicoxyzzy/react,VioletLife/react,billfeller/react,krasimir/react,roth1002/react,quip/react,jzmq/react,yungsters/react,STRML/react,silvestrijonathan/react,wmydz1/react,maxschmeling/react,aickin/react,prometheansacrifice/react,apaatsio/react,yiminghe/react,jorrit/react,leexiaosi/react,jameszhan/react,TheBlasfem/react,Simek/react,acdlite/react,prometheansacrifice/react,flipactual/react,roth1002/react,AlmeroSteyn/react,jquense/react,empyrical/react,yangshun/react,cpojer/react,jzmq/react,quip/react,glenjamin/react,rickbeerendonk/react,flipactual/react,jordanpapaleo/react,joecritch/react,chenglou/react,apaatsio/react,yungsters/react,joecritch/react,ericyang321/react,mhhegazy/react,trueadm/react,camsong/react,ericyang321/react,TheBlasfem/react,apaatsio/react,aickin/react,brigand/react,VioletLife/react,flarnie/react,maxschmeling/react,roth1002/react,cpojer/react,chenglou/react,ericyang321/react,pyitphyoaung/react,rickbeerendonk/react,trueadm/react,AlmeroSteyn/react,nhunzaker/react,prometheansacrifice/react,krasimir/react,empyrical/react,maxschmeling/react,yungsters/react,wmydz1/react,wmydz1/react,yangshun/react,nhunzaker/react,facebook/react,mhhegazy/react,VioletLife/react,chic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