The builder function is not called when it would before the upgrade to the
Flutter version that introduced the optimization.

The UI of a widget is missing.

The UI of a widget is not updating.

Description of change

Prior to the optimization the builder function passed to LayoutBuilder or
SliverLayoutBuilder was called when any one of the following happened:

LayoutBuilder is rebuilt due to a widget configuration change (this typically
happens when the widget that uses LayoutBuilder rebuilds due to setState,
didUpdateWidget or didChangeDependencies).

LayoutBuilder is laid out and receives layout constraints from its parent
that are different from the last received constraints.

LayoutBuilder is laid out and receives layout constraints from its parent
that are the same as the constraints received last time.

After the optimization the builder function is no longer called in the latter
case. If the constraints are the same and the widget configuration did not
change, the builder function is not called.