Adapt and reland old position sticky implementation

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

Index: third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
index a515034a173a1fca281b7d209d74ad448e4d77c1..6f94847c9aa12be6e94b1cb9a9734a98eb8d8b96 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp
@@ -1230,6 +1230,16 @@ void PaintLayerScrollableArea::updateResizerStyle()
     }
 }
 
+void PaintLayerScrollableArea::invalidateStickyConstraints()
+{
+    if (PaintLayerScrollableAreaRareData* d = rareData()) {
+        for (auto& iter : d->m_stickyConstraintsMap) {
+            iter.key->setNeedsCompositingInputsUpdate();
+        }
+        d->m_stickyConstraintsMap.clear();
+    }
+}
+
 IntSize PaintLayerScrollableArea::offsetFromResizeCorner(const IntPoint& absolutePoint) const
 {
     // Currently the resize corner is either the bottom right corner or the bottom left corner.