Specs: (reverts part of recent checkin) Make appendChild, prependChild, and setChild not return the child, since that can improve perf (especially if they're actually implemented natively)
Specs: (reverts part of recent checkin) Make appendChild, prependChild, and setChild not return the child, since that can improve perf (especially if they're actually implemented natively)

Review URL: https://codereview.chromium.org/924163004

tvolkert/engine,zhangxq5012/sky_engine,axinging/sky_engine,takaaptech/sky_engine,krisgiesing/sky_engine,takaaptech/sky_engine,iansf/sky_engine,jamesr/sky_engine,TribeMedia/sky_engine,lyceel/engine,iansf/sky_engine,chinmaygarde/flutter_engine,jimsimon/sky_engine,mdakin/engine,Hixie/sky_engine,mpcomplete/flutter_engine,chinmaygarde/flutter_engine,qiankunshe/sky_engine,mikejurka/engine,mikejurka/engine,jamesr/sky_engine,rmacnak-google/engine,jason-simmons/flutter_engine,jimsimon/sky_engine,mpcomplete/flutter_engine,xunmengfeng/engine,lyceel/engine,chinmaygarde/sky_engine,mpcomplete/engine,lyceel/engine,devoncarew/sky_engine,krisgiesing/sky_engine,lyceel/engine,mxia/engine,jimsimon/sky_engine,jimsimon/sky_engine,tvolkert/engine,mdakin/engine,afandria/sky_engine,Hixie/sky_engine,afandria/sky_engine,cdotstout/sky_engine,jimsimon/sky_engine,abarth/sky_engine,devoncarew/sky_engine,devoncarew/engine,cdotstout/sky_engine,jason-simmons/flutter_engine,jason-simmons/flutter_engine,Hixie/sky_engine,takaaptech/sky_engine,mpcomplete/engine,mdakin/engine,iansf/sky_engine,axinging/sky_engine,jamesr/flutter_engine,devoncarew/engine,takaaptech/sky_engine,tvolkert/engine,TribeMedia/sky_engine,jason-simmons/flutter_engine,flutter/engine,zhangxq5012/sky_engine,flutter/engine,mpcomplete/flutter_engine,qiankunshe/sky_engine,krisgiesing/sky_engine,TribeMedia/sky_engine,mdakin/engine,afandria/sky_engine,chinmaygarde/flutter_engine,mpcomplete/engine,jason-simmons/sky_engine,iansf/sky_engine,iansf/sky_engine,takaaptech/sky_engine,xunmengfeng/engine,devoncarew/sky_engine,devoncarew/sky_engine,chinmaygarde/sky_engine,abarth/sky_engine,aam/engine,chinmaygarde/flutter_engine,mpcomplete/engine,iansf/sky_engine,aam/engine,lyceel/engine,tvolkert/engine,axinging/sky_engine,mikejurka/engine,mpcomplete/engine,devoncarew/sky_engine,mpcomplete/flutter_engine,mxia/engine,chinmaygarde/sky_engine,qiankunshe/sky_engine,jimsimon/sky_engine,axinging/sky_engine,rmacnak-google/engine,abarth/sky_engine,krisgiesing/sky_engine,jamesr/flutter_engine,cdotstout/sky_engine,tvolkert/engine,lyceel/engine,axinging/sky_engine,abarth/sky_engine,TribeMedia/sky_engine,mxia/engine,jason-simmons/flutter_engine,mxia/engine,jamesr/flutter_engine,jamesr/flutter_engine,flutter/engine,mpcomplete/flutter_engine,mikejurka/engine,chinmaygarde/sky_engine,jamesr/flutter_engine,zhangxq5012/sky_engine,jamesr/sky_engine,takaaptech/sky_engine,zhangxq5012/sky_engine,tvolkert/engine,jason-simmons/sky_engine,iansf/sky_engine,axinging/sky_engine,jamesr/flutter_engine,takaaptech/sky_engine,Hixie/sky_engine,chinmaygarde/sky_engine,jamesr/sky_engine,chinmaygarde/flutter_engine,flutter/engine,rmacnak-google/engine,jamesr/sky_engine,zhangxq5012/sky_engine,devoncarew/sky_engine,jason-simmons/flutter_engine,zhangxq5012/sky_engine,jason-simmons/sky_engine,mxia/engine,devoncarew/engine,afandria/sky_engine,mpcomplete/flutter_engine,aam/engine,axinging/sky_engine,jimsimon/sky_engine,axinging/sky_engine,rmacnak-google/engine,jamesr/flutter_engine,xunmengfeng/engine,mpcomplete/engine,mdakin/engine,krisgiesing/sky_engine,mikejurka/engine,chinmaygarde/sky_engine,flutter/engine,jason-simmons/sky_engine,devoncarew/sky_engine,qiankunshe/sky_engine,devoncarew/engine,jason-simmons/sky_engine,afandria/sky_engine,chinmaygarde/flutter_engine,qiankunshe/sky_engine,mxia/engine,aam/engine,aam/engine,jimsimon/sky_engine,zhangxq5012/sky_engine,cdotstout/sky_engine,mpcomplete/engine,abarth/sky_engine,chinmaygarde/sky_engine,TribeMedia/sky_engine,jamesr/flutter_engine,qiankunshe/sky_engine,qiankunshe/sky_engine,rmacnak-google/engine,lyceel/engine,mdakin/engine,axinging/sky_engine,flutter/engine,Hixie/sky_engine,devoncarew/engine,mikejurka/engine,aam/engine,afandria/sky_engine,mpcomplete/engine,TribeMedia/sky_engine,takaaptech/sky_engine,jason-simmons/flutter_engine,mikejurka/engine,jamesr/sky_engine,jason-simmons/sky_engine,rmacnak-google/engine,jason-simmons/sky_engine,aam/engine,cdotstout/sky_engine,abarth/sky_engine,Hixie/sky_engine,mikejurka/engine,devoncarew/engine,iansf/sky_engine,mxia/engine,zhangxq5012/sky_engine,afandria/sky_engine,TribeMedia/sky_engine,mdakin/engine,TribeMedia/sky_engine,flutter/engine,afandria/sky_engine,mdakin/engine,takaaptech/sky_engine,cdotstout/sky_engine,krisgiesing/sky_engine,Hixie/sky_engine,abarth/sky_engine,Hixie/sky_engine,flutter/engine,jamesr/sky_engine,zhangxq5012/sky_engine,mikejurka/engine,cdotstout/sky_engine,xunmengfeng/engine,devoncarew/engine,krisgiesing/sky_engine,xunmengfeng/engine,rmacnak-google/engine,aam/engine,tvolkert/engine,chinmaygarde/flutter_engine,xunmengfeng/engine,mxia/engine,TribeMedia/sky_engine,jimsimon/sky_engine,qiankunshe/sky_engine,jason-simmons/flutter_engine,xunmengfeng/engine,jamesr/flutter_engine