chore: remove dead draggable region code (#38404)

shell/browser/ui/drag_util.h

@@ -10,7 +10,6 @@
 
 #include "shell/common/api/api.mojom.h"
 #include "third_party/skia/include/core/SkRegion.h"
-#include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/image/image.h"
 
 namespace base {
@@ -23,11 +22,6 @@ void DragFileItems(const std::vector<base::FilePath>& files,
                    const gfx::Image& icon,
                    gfx::NativeView view);
 
-std::vector<gfx::Rect> CalculateNonDraggableRegions(
-    std::unique_ptr<SkRegion> draggable,
-    int width,
-    int height);
-
 // Convert draggable regions in raw format to SkRegion format.
 std::unique_ptr<SkRegion> DraggableRegionsToSkRegion(
     const std::vector<mojom::DraggableRegionPtr>& regions);