LibWeb: Fix clip of hidden overflow when translated boxes are involved

There is a problem with current approach where overflow clip rectange is
calculated by aggregating intersection of absolute padding boxes of
boxes in containing block chain that resulting rectangle doesn't
respect transform properties.

To solve this problem `PaintableBox` is changed to store clip rectangle
saved from painter because it does respect transform properties of all
previously applied clip rectangles.

Userland/Libraries/LibGfx/Painter.h

@@ -177,6 +177,7 @@ public:
     }
 
     IntRect clip_rect() const { return state().clip_rect; }
+    void set_clip_rect(IntRect const& rect) { state().clip_rect = rect; }
 
     int scale() const { return state().scale; }