IconGroup: Refactor the canvas resize logic

Move the code to resize the IconGroup canvas to a funtion to be able to
reuse it.

Refactor, no functional changes.

src/Widgets/IconGroup.vala

@@ -96,17 +96,12 @@ namespace Gala {
         }
 
         construct {
-            var scale = InternalUtils.get_ui_scaling_factor ();
-            var size = SIZE * scale;
-
-            width = size;
-            height = size;
             reactive = true;
 
             var canvas = new Canvas ();
-            canvas.set_size (size, size);
             canvas.draw.connect (draw);
             content = canvas;
+            resize_canvas ();
 
             dummy_material = new Cogl.Material ();
 
@@ -202,6 +197,16 @@ namespace Gala {
                 close_button.visible = false;
         }
 
+        bool resize_canvas () {
+            var scale = InternalUtils.get_ui_scaling_factor ();
+            var size = SIZE * scale;
+
+            width = size;
+            height = size;
+
+            return ((Canvas) content).set_size (size, size);
+        }
+
         /**
          * Override the paint handler to draw our backdrop if necessary
          */