SliverGridDelegateWithMaxCrossAxisExtent constructor
Creates a delegate that makes grid layouts with tiles that have a maximum cross-axis extent.
All of the arguments must not be null. The maxCrossAxisExtent and
mainAxisSpacing, and crossAxisSpacing arguments must not be negative.
The childAspectRatio argument must be greater than zero.
Implementation
const SliverGridDelegateWithMaxCrossAxisExtent({
  @required this.maxCrossAxisExtent,
  this.mainAxisSpacing = 0.0,
  this.crossAxisSpacing = 0.0,
  this.childAspectRatio = 1.0,
}) : assert(maxCrossAxisExtent != null && maxCrossAxisExtent >= 0),
     assert(mainAxisSpacing != null && mainAxisSpacing >= 0),
     assert(crossAxisSpacing != null && crossAxisSpacing >= 0),
     assert(childAspectRatio != null && childAspectRatio > 0);