The MatrixClipTracker was nothing more than a vector of MatrixClipState objects and a whole lot of duplicate delegation methods. It provided little value since nearly every use of it already had a state stack that was kept in synch with it's internal stack and so it was just adding an extra layer of delegation and extra allocations.
Flow is a simple compositor based on Skia that the Flutter engine uses to cache
recorded paint commands and pixels generated from those recordings. Flow runs on
the raster thread and uploads information to Skia.