Fix under-invalidation of frame scrollbar on hover

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"
 #include "core/layout/LayoutScrollbarPart.h"
 #include "core/layout/PaintInvalidationState.h"
 #include "core/paint/PaintLayer.h"
 #include "platform/graphics/GraphicsLayer.h"
 
 namespace blink {
 
 void PaintInvalidationCapableScrollableArea::willRemoveScrollbar(Scrollbar& scrollbar, ScrollbarOrientation orientation)
 {
     if (!scrollbar.isCustomScrollbar()
         && !(orientation == HorizontalScrollbar ? layerForHorizontalScrollbar() : layerForVerticalScrollbar()))
-        boxForScrollControlPaintInvalidation().slowSetPaintingLayerNeedsRepaintAndInvalidateDisplayItemClient(scrollbar, PaintInvalidationScroll);
+        layoutBox()->slowSetPaintingLayerNeedsRepaintAndInvalidateDisplayItemClient(scrollbar, PaintInvalidationScroll);
 
     ScrollableArea::willRemoveScrollbar(scrollbar, orientation);
 }
 
 static LayoutRect scrollControlPaintInvalidationRect(const IntRect& scrollControlRect, const LayoutBox& box, const PaintInvalidationState& paintInvalidationState)
 {
     LayoutRect paintInvalidationRect(scrollControlRect);
     if (!paintInvalidationRect.isEmpty())
         paintInvalidationState.mapLocalRectToPaintInvalidationBacking(paintInvalidationRect);
     return paintInvalidationRect;
 }
 
 // Returns true if the scroll control is invalidated.
 static bool invalidatePaintOfScrollControlIfNeeded(const LayoutRect& newPaintInvalidationRect, const LayoutRect& previousPaintInvalidationRect, bool needsPaintInvalidation, LayoutBox& box, const LayoutBoxModelObject& paintInvalidationContainer)
 {
     bool shouldInvalidateNewRect = needsPaintInvalidation;
     if (newPaintInvalidationRect != previousPaintInvalidationRect) {
         box.invalidatePaintUsingContainer(paintInvalidationContainer, previousPaintInvalidationRect, PaintInvalidationScroll);
         shouldInvalidateNewRect = true;
     }
     if (shouldInvalidateNewRect) {
         box.invalidatePaintUsingContainer(paintInvalidationContainer, newPaintInvalidationRect, PaintInvalidationScroll);
-        box.enclosingLayer()->setNeedsRepaint();
         return true;
     }
     return false;
 }
 
 static void invalidatePaintOfScrollbarIfNeeded(Scrollbar* scrollbar, GraphicsLayer* graphicsLayer, bool& previouslyWasOverlay, LayoutRect& previousPaintInvalidationRect, bool needsPaintInvalidationArg, LayoutBox& box, const PaintInvalidationState& paintInvalidationState)
 {
     bool isOverlay = scrollbar && scrollbar->isOverlayScrollbar();
 
     // Calculate paint invalidation rect of the scrollbar, except overlay composited scrollbars because we invalidate the graphics layer only.
@@ skipping 36 matching lines @@
     if (!invalidated || !scrollbar || graphicsLayer)
         return;
 
     box.setPaintingLayerNeedsRepaintAndInvalidateDisplayItemClient(paintInvalidationState, *scrollbar, PaintInvalidationScroll);
     if (scrollbar->isCustomScrollbar())
         toLayoutScrollbar(scrollbar)->invalidateDisplayItemClientsOfScrollbarParts();
 }
 
 void PaintInvalidationCapableScrollableArea::invalidatePaintOfScrollControlsIfNeeded(const PaintInvalidationState& paintInvalidationState)
 {
-    LayoutBox& box = boxForScrollControlPaintInvalidation();
+    LayoutBox& box = *layoutBox();
     invalidatePaintOfScrollbarIfNeeded(horizontalScrollbar(), layerForHorizontalScrollbar(), m_horizontalScrollbarPreviouslyWasOverlay, m_horizontalScrollbarPreviousPaintInvalidationRect, horizontalScrollbarNeedsPaintInvalidation(), box, paintInvalidationState);
     invalidatePaintOfScrollbarIfNeeded(verticalScrollbar(), layerForVerticalScrollbar(), m_verticalScrollbarPreviouslyWasOverlay, m_verticalScrollbarPreviousPaintInvalidationRect, verticalScrollbarNeedsPaintInvalidation(), box, paintInvalidationState);
 
     LayoutRect scrollCornerPaintInvalidationRect = scrollControlPaintInvalidationRect(scrollCornerAndResizerRect(), box, paintInvalidationState);
     const LayoutBoxModelObject& paintInvalidationContainer = paintInvalidationState.paintInvalidationContainer();
     if (invalidatePaintOfScrollControlIfNeeded(scrollCornerPaintInvalidationRect, m_scrollCornerAndResizerPreviousPaintInvalidationRect, scrollCornerNeedsPaintInvalidation(), box, paintInvalidationContainer)) {
         m_scrollCornerAndResizerPreviousPaintInvalidationRect = scrollCornerPaintInvalidationRect;
         if (LayoutScrollbarPart* scrollCorner = this->scrollCorner())
             scrollCorner->invalidateDisplayItemClientsIncludingNonCompositingDescendants(PaintInvalidationScroll);
         if (LayoutScrollbarPart* resizer = this->resizer())
@@ skipping 11 matching lines @@
 }
 
 LayoutRect PaintInvalidationCapableScrollableArea::visualRectForScrollbarParts() const
 {
     LayoutRect fullBounds(m_horizontalScrollbarPreviousPaintInvalidationRect);
     fullBounds.unite(m_verticalScrollbarPreviousPaintInvalidationRect);
     fullBounds.unite(m_scrollCornerAndResizerPreviousPaintInvalidationRect);
     return fullBounds;
 }
 
+void PaintInvalidationCapableScrollableArea::scrollControlWasSetNeedsPaintInvalidation()
+{
+    layoutBox()->setMayNeedPaintInvalidation();
+}
+
 } // namespace blink