Replace original background widget

Replace the widget responsible for drawing the
background with a new stateless widget called
BubbleBackground. Include a colors property to 
represent the full-screen gradient that should be
applied to the bubble.

Create a custom painter

Provide access to scrolling information

Paint a full-screen bubble gradient

Congratulations! You now have a modern, chat bubble UI.

Note:
  The recipe doesn’t yet work on the web because
  Flutter doesn’t yet support Paint shaders.

InheritedWidget documentation
  for more information about these types of dependencies.

Recap