CONSOLE WARNING: Calling Element.createShadowRoot() for an element which already hosts a shadow root is deprecated. See https://www.chromestatus.com/features/4668884095336448 for more details. Flat Tree will be: DIV id=sandbox DIV id=top DIV id=A DIV id=B DIV id=D DIV id=F Moving mouse from B to A mouseout @B (target: B) (related: A) @C (target: B) (related: A) @older-shadow-root (target: B) (related: A) @E (target: B) (related: A) @younger-shadow-root (target: B) (related: A) @A (target: B) (related: A) @top (target: B) (related: A) @[object Window] (target: B) (related: A) mouseover @A (target: A) (related: B) @top (target: A) (related: B) @[object Window] (target: A) (related: B) Moving mouse from A to A/D mouseout mouseover @D (target: D) (related: A) @older-shadow-root (target: D) (related: A) @E (target: D) (related: A) @younger-shadow-root (target: D) (related: A) Moving mouse from A/D to A//F mouseout @D (target: D) (related: A) @older-shadow-root (target: D) (related: A) @E (target: D) (related: F) @younger-shadow-root (target: D) (related: F) mouseover @F (target: F) (related: D) @younger-shadow-root (target: F) (related: D) Moving mouse from B to A//F mouseout @B (target: B) (related: A) @C (target: B) (related: A) @older-shadow-root (target: B) (related: A) @E (target: B) (related: F) @younger-shadow-root (target: B) (related: F) @A (target: B) (related: A) @top (target: B) (related: A) @[object Window] (target: B) (related: A) mouseover @F (target: F) (related: B) @younger-shadow-root (target: F) (related: B) @A (target: A) (related: B) @top (target: A) (related: B) @[object Window] (target: A) (related: B) PASS successfullyParsed is true TEST COMPLETE