Description of change

The actual change modified these APIs to not have a nullOk parameter, and to
return a non-nullable value:

MediaQuery.of

Navigator.of

ScaffoldMessenger.of

Scaffold.of

Router.of

Localizations.localeOf

FocusTraversalOrder.of

FocusTraversalGroup.of

Focus.of

Shortcuts.of

Actions.handler

Actions.find

Actions.invoke

AnimatedList.of

SliverAnimatedList.of

CupertinoDynamicColor.resolve

CupertinoDynamicColor.resolveFrom

CupertinoUserInterfaceLevel.of

CupertinoTheme.brightnessOf