Flutter provides a wide variety of debug flags and functions
to help you debug your app at various points along the
development cycle. To use these features, you must compile
in debug mode.  The following list, while not complete,
highlights some of flags (and one function) from the
rendering library for debugging performance issues.

You can set these flags either by editing the framework code,
or by importing the module and setting the value in your
main() method, following by a hot restart.

debugDumpRenderTree()

Call this function when not in a layout or repaint
  phase to dump the rendering tree to the console.
  (Pressing t from flutter run calls this command.)
  Search for “RepaintBoundary” to see diagnostics
  on how useful a boundary is.

debugPaintLayerBordersEnabled

PENDING

debugRepaintRainbowEnabled