Tracker: Use BControlLook::ComposeIconSize.

One computation was functionally equivalent to the new method,
other places were not scaling icons at all.

Fixes #13177.

headers/private/tracker/IconMenuItem.h

@@ -69,11 +69,8 @@ class IconMenuItem : public PositionPassingMenuItem {
 		virtual void DrawContent();
 		virtual void SetMarked(bool mark);
 
+private:
 		virtual void SetIcon(BBitmap* icon);
-		BBitmap* Icon() const { return fDeviceIcon; };
-
-		virtual void SetIconSize(icon_size which) { fWhich = which; };
-		icon_size IconSize() const { return fWhich; };
 
 	private:
 		BBitmap* fDeviceIcon;