[1.5.4] Upgrade sliver.

Runtime/rendering/sliver.cs

         public readonly bool hasVisualOverflow;
         public readonly float? scrollOffsetCorrection;
         public readonly float cacheExtent;
+        public const float precisionErrorTolerance = 1e-10f;
 
         internal static string _debugCompareFloats(string labelA, float valueA, string labelB, float valueB) {
             if (valueA.ToString("F1") != valueB.ToString("F1")) {
                     );
                 }
 
-                if (this.maxPaintExtent < this.paintExtent) {
+                if (this.paintExtent - this.maxPaintExtent > precisionErrorTolerance) {
                     verify(false,
                         "The \"maxPaintExtent\" is less than the \"paintExtent\".\n" +
                         _debugCompareFloats("maxPaintExtent", this.maxPaintExtent, "paintExtent",

Runtime/rendering/sliver_grid.cs

 
         float _getOffsetFromStartInCrossAxis(float crossAxisStart) {
             if (this.reverseCrossAxis == true) {
-                return (this.crossAxisCount * this.crossAxisStride - crossAxisStart - this.childCrossAxisExtent) ??
+                return (this.crossAxisCount * this.crossAxisStride - crossAxisStart - this.childCrossAxisExtent
+                        - (this.crossAxisStride - this.childCrossAxisExtent)) ??
                        0.0f;
             }
 

Runtime/rendering/sliver_list.cs

                 }
                 else {
                     float firstChildScrollOffset = earliestScrollOffset - this.paintExtentOf(this.firstChild);
-                    if (firstChildScrollOffset < 0.0) {
+                    if (firstChildScrollOffset < -SliverGeometry.precisionErrorTolerance) {
                         float correction = 0.0f;
                         while (earliestUsefulChild != null) {
                             D.assert(this.firstChild == earliestUsefulChild);