Let synchronized painting generate correct paint invalidation rects

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 202 matching lines @@
         return;
 
     if (scrollbar == verticalScrollbar())
         scrollRect.move(verticalScrollbarStart(0, box().size().width()), box().borderTop());
     else
         scrollRect.move(horizontalScrollbarStart(0), box().size().height() - box().borderBottom() - scrollbar->height());
 
     if (scrollRect.isEmpty())
         return;
 
-    box().invalidateDisplayItemClient(*scrollbar);
-
     LayoutRect paintInvalidationRect = LayoutRect(scrollRect);
     box().flipForWritingMode(paintInvalidationRect);
 
     IntRect intRect = pixelSnappedIntRect(paintInvalidationRect);
 
     if (box().frameView()->isInPerformLayout()) {
         addScrollbarDamage(scrollbar, intRect);
     } else {
         // FIXME: We should not allow paint invalidation out of paint invalidation state. crbug.com/457415
         DisablePaintInvalidationStateAsserts disabler;
         // We have invalidated the displayItemClient of the scrollbar, but for now we still need to
         // invalidate the rectangles to trigger repaints.
         box().invalidatePaintRectangleNotInvalidatingDisplayItemClients(LayoutRect(intRect));
+        box().invalidateDisplayItemClient(*scrollbar);
     }
 }
 
 void PaintLayerScrollableArea::invalidateScrollCornerRect(const IntRect& rect)
 {
     ASSERT(!layerForScrollCorner());
 
     if (m_scrollCorner) {
         // FIXME: We should not allow paint invalidation out of paint invalidation state. crbug.com/457415
         DisablePaintInvalidationStateAsserts disabler;
@@ skipping 1312 matching lines @@
     return widget.release();
 }
 
 void PaintLayerScrollableArea::ScrollbarManager::destroyScrollbar(ScrollbarOrientation orientation, bool invalidate)
 {
     RefPtrWillBeMember<Scrollbar>& scrollbar = orientation == HorizontalScrollbar ? m_hBar : m_vBar;
     ASSERT(orientation == HorizontalScrollbar ? !m_hBarIsAttached: !m_vBarIsAttached);
     if (!scrollbar)
         return;
 
-    if (invalidate)
+    if (invalidate) {
+        m_scrollableArea->box().invalidateDisplayItemClient(*scrollbar);
         scrollbar->invalidate();
+    }
     if (!scrollbar->isCustomScrollbar())
         m_scrollableArea->willRemoveScrollbar(scrollbar.get(), orientation);
 
     toFrameView(scrollbar->parent())->removeChild(scrollbar.get());
     scrollbar->disconnectFromScrollableArea();
     scrollbar = nullptr;
 }
 
 DEFINE_TRACE(PaintLayerScrollableArea::ScrollbarManager)
 {
     visitor->trace(m_scrollableArea);
     visitor->trace(m_hBar);
     visitor->trace(m_vBar);
 }
 
 } // namespace blink