rebase https://codereview.chromium.org/1484163002

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/paint/PaintInvalidationCapableScrollableArea.h"
 
 #include "core/frame/Settings.h"
 #include "core/html/HTMLFrameOwnerElement.h"
 #include "core/layout/LayoutBox.h"
 #include "core/layout/LayoutScrollbar.h"
@@ skipping 48 matching lines @@
 
     bool needsPaintInvalidation = needsPaintInvalidationArg;
     if (graphicsLayer) {
         // If the scrollbar needs paint invalidation but didn't change location/size or the scrollbar is an
         // overlay scrollbar (paint invalidation rect is empty), invalidating the graphics layer is enough
         // (which has been done in ScrollableArea::setScrollbarNeedsPaintInvalidation()).
         // Otherwise invalidatePaintOfScrollControlIfNeeded() below will invalidate the old and new location
         // of the scrollbar on the box's paint invalidation container to ensure newly expanded/shrunk areas
         // of the box to be invalidated.
         needsPaintInvalidation = false;
+
+        graphicsLayer->invalidateDisplayItemClient(*graphicsLayer, PaintInvalidationScroll);
     }
 
     // Invalidate the box's display item client if the box's padding box size is affected by change of the
     // non-overlay scrollbar width. We detect change of paint invalidation rect size instead of change of
     // scrollbar width change, which may have some false-positives (e.g. the scrollbar changed length but
     // not width) but won't invalidate more than expected because in the false-positive case the box must
     // have changed size and have been invalidated.
     const LayoutBoxModelObject& paintInvalidationContainer = paintInvalidationState.paintInvalidationContainer();
     LayoutSize newScrollbarUsedSpaceInBox;
     if (!isOverlay)
@@ skipping 45 matching lines @@
 
 LayoutRect PaintInvalidationCapableScrollableArea::visualRectForScrollbarParts() const
 {
     LayoutRect fullBounds(m_horizontalScrollbarPreviousPaintInvalidationRect);
     fullBounds.unite(m_verticalScrollbarPreviousPaintInvalidationRect);
     fullBounds.unite(m_scrollCornerAndResizerPreviousPaintInvalidationRect);
     return fullBounds;
 }
 
 } // namespace blink