Merge branch 'kgdev' into 'master'

more materials.

See merge request upm-packages/ui-widgets/com.unity.uiwidgets!103

Runtime/material/switch.cs

         public override void debugFillProperties(DiagnosticPropertiesBuilder properties) {
             base.debugFillProperties(properties);
             properties.add(new FlagProperty("value", value: this.value, ifTrue: "on", ifFalse: "off", showName: true));
-            properties.add(new ObjectFlagProperty<ValueChanged<bool>>("onChanged", this.onChanged, ifNull: "disabled"));
+            properties.add(new ObjectFlagProperty<ValueChanged<bool?>>("onChanged", this.onChanged, ifNull: "disabled"));
         }
     }
 

Runtime/material/theme_data.cs

             this.iconTheme = iconTheme;
             this.primaryIconTheme = primaryIconTheme;
             this.accentIconTheme = accentIconTheme;
-            this.platform = platform;
+            this.platform = platform.Value;
             this.materialTapTargetSize = materialTapTargetSize ?? MaterialTapTargetSize.padded;
             this.pageTransitionsTheme = pageTransitionsTheme;
             this.colorScheme = colorScheme;

Runtime/material/toggleable.cs

     }
 
     public abstract class RenderToggleable : RenderConstrainedBox {
-        RenderToggleable(
+        protected RenderToggleable(
             bool? value = null,
             bool tristate = false,
             Color activeColor = null,