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

collinjackson/mojo,chinmaygarde/mojo,afandria/mojo,jianglu/mojo,collinjackson/mojo,collinjackson/mojo,collinjackson/mojo,collinjackson/mojo,chinmaygarde/mojo,afandria/mojo,collinjackson/mojo,jianglu/mojo,afandria/mojo,chinmaygarde/mojo,chinmaygarde/mojo,collinjackson/mojo,chinmaygarde/mojo,collinjackson/mojo,collinjackson/mojo,afandria/mojo,jianglu/mojo,jianglu/mojo,jianglu/mojo,afandria/mojo,afandria/mojo,chinmaygarde/mojo,jianglu/mojo,afandria/mojo,jianglu/mojo,afandria/mojo,chinmaygarde/mojo,chinmaygarde/mojo,jianglu/mojo,chinmaygarde/mojo