Bug 1699931 - Fix checked checkbox radius in the non-native theme. r=mstange

This is caused by a minor issue with WebRender disabled where the radii
was slightly off because it wasn't accounting for the deflation of the
rect.

Differential Revision: https://phabricator.services.mozilla.com/D109206

widget/nsNativeBasicTheme.cpp

@@ -851,7 +851,7 @@ void nsNativeBasicTheme::PaintRoundedRectWithRadius(
   // stroke fills exactly the area we want to fill and not more.
   rect.Deflate(borderWidth * 0.5f);
 
-  LayoutDeviceCoord radius(aRadius * aDpiRatio);
+  LayoutDeviceCoord radius(aRadius * aDpiRatio - borderWidth * 0.5f);
   // Fix up the radius if it's too large with the rect we're going to paint.
   {
     LayoutDeviceCoord min = std::min(rect.width, rect.height);