The LayoutGrid class is becoming too big and unmanageable (>3.6k LoC). One of the reasons why it's so big is because it contains all the track sizing algorithm code. Although it looks like it naturally belong to the LayoutGrid object the truth is that it creates some difficulties:

1- requires lots of methods that are used just by the algorithm
2- requires a temporary data structure (GridSizingData) to store the results of the different steps of the algorithm
3- this data structure has to be passed to tons of methods
4- the indefinite/definite behaviour is mixed in method implementations so it's difficult to track the code path for each one

The proposal is the following:
1- Move Grid class out of LayoutGrid
2- Move the track sizing algorithm code to a new class GridTrackSizingAlgorithm
3- Move all the GridSizingData attributes to private members of GridTrackSizingAlgorithm and do not pass it as argument anymore
4- Use a strategy pattern to configure the behaviour of the algorithm for the definite size and indefinite size cases

Once the proposal is implemented, all the track sizing algorithm code will be isolated in a single file. The caller would configure the algorithm (with some setup() method) passing some parameters like the axis (row|columns), the available space, the free space.... After that a run() method will perform the track sizing, and that's it. The LayoutAlgorithm will later use some public API to retrieve the required info.

The track sizing algorithm will delegate any task with different behaviours for indefinite/definite sizes to another class called GridTrackSizingAlgorithmStrategy. That abstract class will have two children: on for definite sizes and another one for indefinite ones. The GridTrackSizingAlgorithm will create the strategy (depending on the values passed to setup()) which will be totally transparent to the client.