Implement position: sticky updates on compositor

cc/blink/web_layer_impl.h

Index: cc/blink/web_layer_impl.h
diff --git a/cc/blink/web_layer_impl.h b/cc/blink/web_layer_impl.h
index 3420d3aff77d9b8bdff58853056cd0cd7e45c0fe..54335ac335f98268f2d377ed9b52a9487cf5cb75 100644
--- a/cc/blink/web_layer_impl.h
+++ b/cc/blink/web_layer_impl.h
@@ -124,6 +124,10 @@ class CC_BLINK_EXPORT WebLayerImpl : public NON_EXPORTED_BASE(blink::WebLayer) {
   void setPositionConstraint(
       const blink::WebLayerPositionConstraint& constraint) override;
   blink::WebLayerPositionConstraint positionConstraint() const override;
+  void setStickyPositionConstraint(
+      const blink::WebLayerStickyPositionConstraint& constraint) override;
+  blink::WebLayerStickyPositionConstraint stickyPositionConstraint()
+      const override;
   void setScrollClient(blink::WebLayerScrollClient* client) override;
   void setLayerClient(cc::LayerClient* client) override;
   const cc::Layer* ccLayer() const override;