--- a/editor/libeditor/EditorBase.cpp
+++ b/editor/libeditor/EditorBase.cpp
@@ -2637,22 +2637,24 @@ EditorBase::InsertTextIntoTextNodeImpl(c
 
 nsresult
 EditorBase::SelectEntireDocument(Selection* aSelection)
 {
   if (!aSelection) {
     return NS_ERROR_NULL_POINTER;
   }
 
-  nsCOMPtr<nsIDOMElement> rootElement = do_QueryInterface(GetRoot());
+  Element* rootElement = GetRoot();
   if (!rootElement) {
     return NS_ERROR_NOT_INITIALIZED;
   }
 
-  return aSelection->SelectAllChildren(rootElement);
+  ErrorResult errorResult;
+  aSelection->SelectAllChildren(*rootElement, errorResult);
+  return errorResult.StealNSResult();
 }
 
 nsINode*
 EditorBase::GetFirstEditableNode(nsINode* aRoot)
 {
   MOZ_ASSERT(aRoot);
 
   nsIContent* node = GetLeftmostChild(aRoot);

--- a/editor/libeditor/HTMLEditor.cpp
+++ b/editor/libeditor/HTMLEditor.cpp
@@ -3609,24 +3609,23 @@ HTMLEditor::SelectAll()
     rootContent = mRootElement;
   } else {
     nsCOMPtr<nsIPresShell> ps = GetPresShell();
     rootContent = anchorContent->GetSelectionRootContent(ps);
   }
 
   NS_ENSURE_TRUE(rootContent, NS_ERROR_UNEXPECTED);
 
-  nsCOMPtr<nsIDOMNode> rootElement = do_QueryInterface(rootContent, &rv);
-  NS_ENSURE_SUCCESS(rv, rv);
-
   Maybe<mozilla::dom::Selection::AutoUserInitiated> userSelection;
   if (!rootContent->IsEditable()) {
     userSelection.emplace(selection);
   }
-  return selection->SelectAllChildren(rootElement);
+  ErrorResult errorResult;
+  selection->SelectAllChildren(*rootContent, errorResult);
+  return errorResult.StealNSResult();
 }
 
 // this will NOT find aAttribute unless aAttribute has a non-null value
 // so singleton attributes like <Table border> will not be matched!
 bool
 HTMLEditor::IsTextPropertySetByContent(nsINode* aNode,
                                        nsIAtom* aProperty,
                                        const nsAString* aAttribute,