minor fixes

com.unity.uiwidgets/Runtime/material/range_slider.cs

             markNeedsLayout();
         }
 
-        protected override void systemFontsDidChange() {
+        public override void systemFontsDidChange() {
             base.systemFontsDidChange();
             _startLabelPainter.markNeedsLayout();
             _endLabelPainter.markNeedsLayout();

com.unity.uiwidgets/Runtime/material/selectable_text.cs

         case RuntimePlatform.OSXEditor:
         case RuntimePlatform.OSXPlayer:
             forcePressEnabled = true;
-            textSelectionControls = CupertinoTextSelectionUtils.cupertinoTextSelectionControls;
+            textSelectionControls = CupertinoTextFieldUtils.cupertinoTextSelectionControls;
             paintCursorAboveText = true;
             cursorOpacityAnimates = true;
             cursorColor = cursorColor ?? CupertinoTheme.of(context).primaryColor;

com.unity.uiwidgets/Runtime/material/slider.cs

             markNeedsLayout();
         }
         
-        protected override void systemFontsDidChange() {
+        public override void systemFontsDidChange() {
                base.systemFontsDidChange();
                 _labelPainter.markNeedsLayout();
                 _updateLabelPainter();