In flutter/engine#48226 , @knopp added a new layer type that may be used by iOS that should have better performance characteristics. As of right now, this is an opt in which can be specified by adding the following flag to the info.plist:

   <key>FLTUseFlutterMetalLayer</key>
  <true/>

This issue tracks enabling this functionality by default. While we did land it off by default due to the proximity to the holidays, now that we're back perhaps we should just turn it on by default and leave it as an opt out?