Calculate paint invalidation rect for scrollbars

third_party/WebKit/Source/core/layout/LayoutScrollbar.cpp

 /*
  * Copyright (C) 2008, 2009 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 183 matching lines @@
         newThickness = isHorizontal ? part->size().height() : part->size().width();
     }
 
     if (newThickness != oldThickness) {
         setFrameRect(IntRect(location(), IntSize(isHorizontal ? width() : newThickness, isHorizontal ? newThickness : height())));
         if (LayoutBox* box = owningLayoutObjectWithinFrame()) {
             if (box->isLayoutBlock())
                 toLayoutBlock(box)->notifyScrollbarThicknessChanged();
             box->setChildNeedsLayout();
             if (m_scrollableArea)
-                m_scrollableArea->invalidateScrollCorner(m_scrollableArea->scrollCornerRect());
+                m_scrollableArea->setScrollCornerNeedsPaintInvalidation();
         }
     }
 }
 
 static PseudoId pseudoForScrollbarPart(ScrollbarPart part)
 {
     switch (part) {
     case BackButtonStartPart:
     case ForwardButtonStartPart:
     case BackButtonEndPart:
@@ skipping 140 matching lines @@
 
 int LayoutScrollbar::minimumThumbLength() const
 {
     LayoutScrollbarPart* partLayoutObject = m_parts.get(ThumbPart);
     if (!partLayoutObject)
         return 0;
     partLayoutObject->layout();
     return orientation() == HorizontalScrollbar ? partLayoutObject->size().width() : partLayoutObject->size().height();
 }
 
-void LayoutScrollbar::invalidateRect(const IntRect& rect)
+void LayoutScrollbar::invalidateDisplayItemClientsOfScrollbarParts(const LayoutBoxModelObject& paintInvalidationContainer, const LayoutRect& paintInvalidationRect)
 {
-    Scrollbar::invalidateRect(rect);
-
-    // FIXME: invalidate only the changed part.
-    if (LayoutBox* owningLayoutObject = this->owningLayoutObject()) {
-        for (auto& part : m_parts)
-            owningLayoutObject->invalidateDisplayItemClientForNonCompositingDescendantsOf(*part.value);
-    }
+    for (auto& part : m_parts)
+        part.value->invalidateDisplayItemClientsIncludingNonCompositingDescendants(&paintInvalidationContainer, PaintInvalidationScroll, &paintInvalidationRect);
 }
 
 }