1 files changed, 19 insertions, 0 deletions
diff --git a/dom/base/Element.cpp b/dom/base/Element.cpp
index 638d6674d2..cd803a60f9 100644
--- a/dom/base/Element.cpp
+++ b/dom/base/Element.cpp
@@ -1104,6 +1104,25 @@ Element::GetSlot(nsAString& aName)
   GetAttr(kNameSpaceID_None, nsGkAtoms::slot, aName);
 }
 
+// https://dom.spec.whatwg.org/#dom-element-shadowroot
+ShadowRoot*
+Element::GetShadowRootByMode() const
+{
+  /**
+   * 1. Let shadow be context object’s shadow root.
+   * 2. If shadow is null or its mode is "closed", then return null.
+   */
+  ShadowRoot* shadowRoot = GetShadowRoot();
+  if (!shadowRoot || shadowRoot->IsClosed()) {
+    return nullptr;
+  }
+
+  /**
+   * 3. Return shadow.
+   */
+  return shadowRoot;
+}
+
 // https://dom.spec.whatwg.org/#dom-element-attachshadow
 already_AddRefed<ShadowRoot>
 Element::AttachShadow(const ShadowRootInit& aInit, ErrorResult& aError)