This is an umbrella task/progress report of this design doc: Using slot to embed web Platform Views.

A partial breakdown of the tasks:

• Wrap contents of scene in a ShadowDOM.
• Add flag to opt-into the new rendering mechanism. DO WE WANT THIS?? NO
• Render views into the DOM in an unified way (this code should be identical both for canvaskit and html backends, since we're rendering outside of the ShadowDOM.
  • Render SLOT on canvaskit backend
  • Render SLOT on html backend
• Testing. WIP PR.