Adapt and reland old position sticky implementation

Source/core/layout/compositing/CompositedDeprecatedPaintLayerMapping.cpp

Index: Source/core/layout/compositing/CompositedDeprecatedPaintLayerMapping.cpp
diff --git a/Source/core/layout/compositing/CompositedDeprecatedPaintLayerMapping.cpp b/Source/core/layout/compositing/CompositedDeprecatedPaintLayerMapping.cpp
index 6d56b078c9263b881ba7e4af5028bffadbf97538..eed12e4fa59f28be2848ee87d383f2d9a01e35d3 100644
--- a/Source/core/layout/compositing/CompositedDeprecatedPaintLayerMapping.cpp
+++ b/Source/core/layout/compositing/CompositedDeprecatedPaintLayerMapping.cpp
@@ -48,6 +48,7 @@
 #include "core/layout/compositing/DeprecatedPaintLayerCompositor.h"
 #include "core/page/ChromeClient.h"
 #include "core/page/Page.h"
+#include "core/page/scrolling/ScrollingConstraints.h"
 #include "core/page/scrolling/ScrollingCoordinator.h"
 #include "core/paint/DeprecatedPaintLayerPainter.h"
 #include "core/paint/DeprecatedPaintLayerStackingNodeIterator.h"
@@ -63,6 +64,7 @@
 #include "platform/graphics/paint/ClipDisplayItem.h"
 #include "platform/graphics/paint/DisplayItemList.h"
 #include "platform/graphics/paint/TransformDisplayItem.h"
+#include "public/platform/WebLayerPositionConstraint.h"
 #include "wtf/CurrentTime.h"
 #include "wtf/text/StringBuilder.h"
 
@@ -229,6 +231,7 @@ void CompositedDeprecatedPaintLayerMapping::createPrimaryGraphicsLayer()
     updateTransform(layoutObject()->styleRef());
     updateFilters(layoutObject()->styleRef());
     updateBackdropFilters(layoutObject()->styleRef());
+    updateStickyConstraints(layoutObject()->styleRef());
 
     if (RuntimeEnabledFeatures::cssCompositingEnabled()) {
         updateLayerBlendMode(layoutObject()->styleRef());
@@ -288,6 +291,45 @@ void CompositedDeprecatedPaintLayerMapping::updateLayerBlendMode(const ComputedS
     setBlendMode(style.blendMode());
 }
 
+void CompositedDeprecatedPaintLayerMapping::updateStickyConstraints(const ComputedStyle& style)
+{
+    bool sticky = style.position() == EPosition::StickyPosition;
+    if (sticky) {
+        const DeprecatedPaintLayer* ancestorScrollingLayer = m_owningLayer.ancestorScrollingLayer();
+        if (ancestorScrollingLayer) {
+            sticky = ancestorScrollingLayer->needsCompositedScrolling();
+        } else {
+            // If there's no ancestor scrolling layer the viewport is our ancestor scroller.
+            sticky = layoutObject()->view()->frameView()->isScrollable();
+        }
+    }
+
+    WebLayerStickyPositionConstraint webConstraint;
+    if (sticky) {
+        LayoutBoxModelObject* boxModelObject = m_owningLayer.layoutObject();
+        LayoutRect containingRect = boxModelObject->computeStickyConstrainingRect();
+        StickyPositionViewportConstraints constraints;
+        boxModelObject->computeStickyPositionConstraints(constraints, containingRect);
+
+        webConstraint.isSticky = true;
+
+        webConstraint.isAnchoredLeft = constraints.anchorEdges() & ViewportConstraints::AnchorEdgeLeft;
+        webConstraint.isAnchoredRight = constraints.anchorEdges() & ViewportConstraints::AnchorEdgeRight;
+        webConstraint.isAnchoredTop = constraints.anchorEdges() & ViewportConstraints::AnchorEdgeTop;
+        webConstraint.isAnchoredBottom = constraints.anchorEdges() & ViewportConstraints::AnchorEdgeBottom;
+
+        webConstraint.leftOffset = constraints.leftOffset().toFloat();
+        webConstraint.rightOffset = constraints.rightOffset().toFloat();
+        webConstraint.topOffset = constraints.topOffset().toFloat();
+        webConstraint.bottomOffset = constraints.bottomOffset().toFloat();
+
+        webConstraint.absoluteStickyBoxRect = enclosingIntRect(constraints.absoluteStickyBoxRect());
+        webConstraint.absoluteContainingBlockRect = enclosingIntRect(constraints.absoluteContainingBlockRect());
+    }
+
+    m_graphicsLayer->platformLayer()->setStickyPositionConstraint(webConstraint);
+}
+
 void CompositedDeprecatedPaintLayerMapping::updateIsRootForIsolatedGroup()
 {
     bool isolate = m_owningLayer.shouldIsolateCompositedDescendants();
@@ -731,6 +773,8 @@ void CompositedDeprecatedPaintLayerMapping::updateGraphicsLayerGeometry(const De
     updateScrollParent(scrollParent());
     registerScrollingLayers();
 
+    updateStickyConstraints(layoutObject()->styleRef());
+
     updateCompositingReasons();
 }