b=444870 no need to increase the cliprect for scrollbar thumbs because the cliprect already includes the extra size r=roc

widget/src/gtk2/gtk2drawing.c

@@ -1335,21 +1335,12 @@ moz_gtk_scrollbar_thumb_paint(GtkThemeWidgetType widget,
        surrounding the scrollbar if the theme thinks that it's butted
        up against the scrollbar arrows.  Note the increases of the
        clip rect below. */
-    /* Changing the cliprect is pretty bogus. This lets themes draw
-       outside the frame, which means we don't invalidate them
-       correctly. See bug 297508. But some themes do seem to need
-       it. So we modify the frame's overflow area to account for what
-       we're doing here; see nsNativeThemeGTK::GetWidgetOverflow. */
     adj = gtk_range_get_adjustment(GTK_RANGE(scrollbar));
 
     if (widget == MOZ_GTK_SCROLLBAR_THUMB_HORIZONTAL) {
-        cliprect->x -= 1;
-        cliprect->width += 2;
         adj->page_size = rect->width;
     }
     else {
-        cliprect->y -= 1;
-        cliprect->height += 2;
         adj->page_size = rect->height;
     }
 

widget/src/gtk2/nsNativeThemeGTK.cpp

@@ -662,7 +662,7 @@ GetExtraSizeForWidget(PRUint8 aWidgetType, PRBool aWidgetIsDefault,
   *aExtra = nsIntMargin(0,0,0,0);
   // Allow an extra one pixel above and below the thumb for certain
   // GTK2 themes (Ximian Industrial, Bluecurve, Misty, at least);
-  // see moz_gtk_scrollbar_thumb_paint in gtk2drawing.c
+  // We modify the frame's overflow area.  See bug 297508.
   switch (aWidgetType) {
   case NS_THEME_SCROLLBAR_THUMB_VERTICAL:
     aExtra->top = aExtra->bottom = 1;