Implement an opaque Size type

It immutably ties physical and logical sizes to a specific scale factor.

winit/src/size.rs

@@ -0,0 +1,30 @@
+pub struct Size {
+    physical: winit::dpi::PhysicalSize<u32>,
+    logical: winit::dpi::LogicalSize<f64>,
+    scale_factor: f64,
+}
+
+impl Size {
+    pub fn new(
+        physical: winit::dpi::PhysicalSize<u32>,
+        scale_factor: f64,
+    ) -> Size {
+        Size {
+            logical: physical.to_logical(scale_factor),
+            physical,
+            scale_factor,
+        }
+    }
+
+    pub fn physical(&self) -> winit::dpi::PhysicalSize<u32> {
+        self.physical
+    }
+
+    pub fn logical(&self) -> winit::dpi::LogicalSize<f64> {
+        self.logical
+    }
+
+    pub fn scale_factor(&self) -> f64 {
+        self.scale_factor
+    }
+}