Rudimentary fix for devicePixelRatio (#365)

Tries to mirror changes made in flutter/flutter PR 126535 for devicePixelRatio

Does not mirror changes made to scroll_position.dart

  @override
  double get devicePixelRatio => context.devicePixelRatio;

@@ -392,6 +392,8 @@ class SheetState extends State<SheetScrollable>
 
 
   @override
   @override
   void didChangeDependencies() {
   void didChangeDependencies() {
+    _devicePixelRatio = MediaQuery.maybeDevicePixelRatioOf(context) ??
+        View.of(context).devicePixelRatio;
     _updatePosition();
     _updatePosition();
     super.didChangeDependencies();
     super.didChangeDependencies();
   }
   }
@@ -560,6 +562,10 @@ class SheetState extends State<SheetScrollable>
   TickerProvider get vsync => this;
   TickerProvider get vsync => this;
 
 
   @override
   @override
+  double get devicePixelRatio => _devicePixelRatio;
+  late double _devicePixelRatio;
+
+  @override
   @protected
   @protected
   void setIgnorePointer(bool value) {
   void setIgnorePointer(bool value) {
     if (_shouldIgnorePointer == value) return;
     if (_shouldIgnorePointer == value) return;