--- a/editor/libeditor/EditorBase.cpp
+++ b/editor/libeditor/EditorBase.cpp
@@ -1128,37 +1128,46 @@ EditorBase::BeginningOfDocument()
 
   int32_t offsetInParent = parent->IndexOf(firstNode);
   return selection->Collapse(parent, offsetInParent);
 }
 
 NS_IMETHODIMP
 EditorBase::EndOfDocument()
 {
+  RefPtr<Selection> selection = GetSelection();
+  return CollapseSelectionToEnd(selection);
+}
+
+nsresult
+EditorBase::CollapseSelectionToEnd(Selection* aSelection)
+{
   // XXX Why doesn't this check if the document is alive?
   if (NS_WARN_IF(!IsInitialized())) {
     return NS_ERROR_NOT_INITIALIZED;
   }
 
-  // get selection
-  RefPtr<Selection> selection = GetSelection();
-  NS_ENSURE_TRUE(selection, NS_ERROR_NULL_POINTER);
+  if (NS_WARN_IF(!aSelection)) {
+    return NS_ERROR_NULL_POINTER;
+  }
 
   // get the root element
   nsINode* node = GetRoot();
-  NS_ENSURE_TRUE(node, NS_ERROR_NULL_POINTER);
+  if (NS_WARN_IF(!node)) {
+    return NS_ERROR_NULL_POINTER;
+  }
+
   nsINode* child = node->GetLastChild();
-
-  while (child && IsContainer(child->AsDOMNode())) {
+  while (child && IsContainer(child)) {
     node = child;
     child = node->GetLastChild();
   }
 
   uint32_t length = node->Length();
-  return selection->Collapse(node, int32_t(length));
+  return aSelection->Collapse(node, static_cast<int32_t>(length));
 }
 
 NS_IMETHODIMP
 EditorBase::GetDocumentModified(bool* outDocModified)
 {
   NS_ENSURE_TRUE(outDocModified, NS_ERROR_NULL_POINTER);
 
   int32_t  modCount = 0;

--- a/editor/libeditor/EditorBase.h
+++ b/editor/libeditor/EditorBase.h
@@ -900,16 +900,21 @@ public:
     if (!sc) {
       return nullptr;
     }
     Selection* selection = sc->GetDOMSelection(ToRawSelectionType(aSelectionType));
     return selection;
   }
 
   /**
+   * CollapseSelectionToEnd() collapses the selection to the end of the editor.
+   */
+  nsresult CollapseSelectionToEnd(Selection* aSelection);
+
+  /**
    * Helpers to add a node to the selection.
    * Used by table cell selection methods.
    */
   nsresult CreateRange(nsIDOMNode* aStartContainer, int32_t aStartOffset,
                        nsIDOMNode* aEndContainer, int32_t aEndOffset,
                        nsRange** aRange);
 
   /**

--- a/editor/libeditor/TextEditRules.cpp
+++ b/editor/libeditor/TextEditRules.cpp
@@ -131,17 +131,17 @@ TextEditRules::Init(TextEditor* aTextEdi
   NS_ENSURE_SUCCESS(rv, rv);
 
   // If the selection hasn't been set up yet, set it up collapsed to the end of
   // our editable content.
   int32_t rangeCount;
   rv = selection->GetRangeCount(&rangeCount);
   NS_ENSURE_SUCCESS(rv, rv);
   if (!rangeCount) {
-    rv = mTextEditor->EndOfDocument();
+    rv = mTextEditor->CollapseSelectionToEnd(selection);
     NS_ENSURE_SUCCESS(rv, rv);
   }
 
   if (IsPlaintextEditor()) {
     // ensure trailing br node
     rv = CreateTrailingBRIfNeeded();
     NS_ENSURE_SUCCESS(rv, rv);
   }
@@ -477,17 +477,17 @@ TextEditRules::CollapseSelectionToTraili
   }
 
   NS_ENSURE_STATE(mTextEditor);
 
   // If there is no selection ranges, we should set to the end of the editor.
   // This is usually performed in TextEditRules::Init(), however, if the
   // editor is reframed, this may be called by AfterEdit().
   if (!aSelection->RangeCount()) {
-    mTextEditor->EndOfDocument();
+    mTextEditor->CollapseSelectionToEnd(aSelection);
   }
 
   // if we are at the end of the textarea, we need to set the
   // selection to stick to the mozBR at the end of the textarea.
   int32_t selOffset;
   nsCOMPtr<nsINode> selNode;
   nsresult rv =
     EditorBase::GetStartNodeAndOffset(aSelection,