Base class for data associated with a RenderObject by its parent.
Some render objects wish to store data on their children, such as the
children's input parameters to the parent's layout algorithm or the
children's position relative to other children.
The hash code for this object. [...]
A representation of the runtime type of the object.
Called when the RenderObject is removed from the tree.
Invoked when a non-existent method or property is accessed. [...]
A string representation of this object. [...]