2 files changed, 31 insertions, 4 deletions
diff --git a/dom/base/nsINode.cpp b/dom/base/nsINode.cpp
index 212110b72..355bf0ebf 100644
--- a/dom/base/nsINode.cpp
+++ b/dom/base/nsINode.cpp
@@ -107,6 +107,7 @@
 #include "GeometryUtils.h"
 #include "nsIAnimationObserver.h"
 #include "nsChildContentList.h"
+#include "mozilla/dom/NodeBinding.h"
 
 #ifdef ACCESSIBILITY
 #include "mozilla/dom/AccessibleNode.h"
@@ -250,6 +251,30 @@ nsINode::GetTextEditorRootContent(nsIEditor** aEditor)
   return nullptr;
 }
 
+nsINode* nsINode::GetRootNode(const GetRootNodeOptions& aOptions)
+{
+  if (aOptions.mComposed) {
+    if (IsInComposedDoc() && GetComposedDoc()) {
+      return OwnerDoc();
+    }
+
+    nsINode* node = this;
+    ShadowRoot* shadowRootParent = nullptr;
+    while(node) {
+      node = node->SubtreeRoot();
+      shadowRootParent = ShadowRoot::FromNode(node);
+      if (!shadowRootParent) {
+         break;
+      }
+      node = shadowRootParent->GetHost();
+    }
+
+    return node;
+  }
+
+  return SubtreeRoot();
+}
+
 nsINode*
 nsINode::SubtreeRoot() const
 {
diff --git a/dom/base/nsINode.h b/dom/base/nsINode.h
index d82f5f899..43d44db60 100644
--- a/dom/base/nsINode.h
+++ b/dom/base/nsINode.h
@@ -83,6 +83,7 @@ template<typename> class Sequence;
 class Text;
 class TextOrElementOrDocument;
 struct DOMPointInit;
+struct GetRootNodeOptions;
 } // namespace dom
 } // namespace mozilla
 
@@ -942,10 +943,11 @@ public:
    */
   nsINode* SubtreeRoot() const;
 
-  nsINode* RootNode() const
-  {
-    return SubtreeRoot();
-  }
+  /*
+   * Get context object's shadow-including root if options's composed is true,
+   * and context object's root otherwise.
+   */
+  nsINode* GetRootNode(const mozilla::dom::GetRootNodeOptions& aOptions);
 
   /**
    * See nsIDOMEventTarget