--- a/editor/libeditor/HTMLEditor.cpp
+++ b/editor/libeditor/HTMLEditor.cpp
@@ -18,17 +18,16 @@
 #include "HTMLEditUtils.h"
 #include "HTMLURIRefObject.h"
 #include "StyleSheetTransactions.h"
 #include "TextEditUtils.h"
 #include "TypeInState.h"
 
 #include "nsIDOMText.h"
 #include "nsIDOMMozNamedAttrMap.h"
-#include "nsIDOMNodeList.h"
 #include "nsIDOMDocument.h"
 #include "nsIDOMAttr.h"
 #include "nsIDocumentInlines.h"
 #include "nsIDOMEventTarget.h"
 #include "nsIDOMMouseEvent.h"
 #include "nsIDOMHTMLAnchorElement.h"
 #include "nsISelectionController.h"
 #include "nsIDOMHTMLDocument.h"

--- a/editor/libeditor/TextEditRules.cpp
+++ b/editor/libeditor/TextEditRules.cpp
@@ -25,17 +25,16 @@
 #include "nsError.h"
 #include "nsGkAtoms.h"
 #include "nsIContent.h"
 #include "nsIDOMDocument.h"
 #include "nsIDOMElement.h"
 #include "nsIDOMNode.h"
 #include "nsIDOMNodeFilter.h"
 #include "nsIDOMNodeIterator.h"
-#include "nsIDOMNodeList.h"
 #include "nsIDOMText.h"
 #include "nsNameSpaceManager.h"
 #include "nsINode.h"
 #include "nsIPlaintextEditor.h"
 #include "nsISupportsBase.h"
 #include "nsLiteralString.h"
 #include "nsUnicharUtils.h"
 #include "nsIHTMLCollection.h"

--- a/editor/libeditor/TextEditor.cpp
+++ b/editor/libeditor/TextEditor.cpp
@@ -32,17 +32,16 @@
 #include "nsGkAtoms.h"
 #include "nsIClipboard.h"
 #include "nsIContent.h"
 #include "nsIContentIterator.h"
 #include "nsIDOMDocument.h"
 #include "nsIDOMElement.h"
 #include "nsIDOMEventTarget.h"
 #include "nsIDOMNode.h"
-#include "nsIDOMNodeList.h"
 #include "nsIDocumentEncoder.h"
 #include "nsIEditRules.h"
 #include "nsINode.h"
 #include "nsIPresShell.h"
 #include "nsISelectionController.h"
 #include "nsISupportsPrimitives.h"
 #include "nsITransferable.h"
 #include "nsIWeakReferenceUtils.h"
@@ -227,74 +226,69 @@ TextEditor::EndEditorInit()
 
 NS_IMETHODIMP
 TextEditor::SetDocumentCharacterSet(const nsACString& characterSet)
 {
   nsresult rv = EditorBase::SetDocumentCharacterSet(characterSet);
   NS_ENSURE_SUCCESS(rv, rv);
 
   // Update META charset element.
-  nsCOMPtr<nsIDOMDocument> domdoc = GetDOMDocument();
-  NS_ENSURE_TRUE(domdoc, NS_ERROR_NOT_INITIALIZED);
+  nsCOMPtr<nsIDocument> doc = GetDocument();
+  if (NS_WARN_IF(!doc)) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
 
-  if (UpdateMetaCharset(domdoc, characterSet)) {
+  if (UpdateMetaCharset(*doc, characterSet)) {
     return NS_OK;
   }
 
-  nsCOMPtr<nsIDOMNodeList> headList;
-  rv = domdoc->GetElementsByTagName(NS_LITERAL_STRING("head"), getter_AddRefs(headList));
-  NS_ENSURE_SUCCESS(rv, rv);
-  NS_ENSURE_TRUE(headList, NS_OK);
+  RefPtr<nsContentList> headList =
+    doc->GetElementsByTagName(NS_LITERAL_STRING("head"));
+  if (NS_WARN_IF(!headList)) {
+    return NS_OK;
+  }
 
-  nsCOMPtr<nsIDOMNode> headNode;
-  headList->Item(0, getter_AddRefs(headNode));
-  NS_ENSURE_TRUE(headNode, NS_OK);
+  nsCOMPtr<nsIContent> headNode = headList->Item(0);
+  if (NS_WARN_IF(!headNode)) {
+    return NS_OK;
+  }
 
   // Create a new meta charset tag
-  nsCOMPtr<nsIDOMNode> resultNode;
-  rv = CreateNode(NS_LITERAL_STRING("meta"), headNode, 0, getter_AddRefs(resultNode));
-  NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
-  NS_ENSURE_TRUE(resultNode, NS_OK);
+  RefPtr<Element> metaElement = CreateNode(nsGkAtoms::meta, headNode, 0);
+  if (NS_WARN_IF(!metaElement)) {
+    return NS_OK;
+  }
 
   // Set attributes to the created element
   if (characterSet.IsEmpty()) {
     return NS_OK;
   }
 
-  nsCOMPtr<dom::Element> metaElement = do_QueryInterface(resultNode);
-  if (!metaElement) {
-    return NS_OK;
-  }
-
   // not undoable, undo should undo CreateNode
   metaElement->SetAttr(kNameSpaceID_None, nsGkAtoms::httpEquiv,
                        NS_LITERAL_STRING("Content-Type"), true);
   metaElement->SetAttr(kNameSpaceID_None, nsGkAtoms::content,
                        NS_LITERAL_STRING("text/html;charset=") +
                          NS_ConvertASCIItoUTF16(characterSet),
                        true);
   return NS_OK;
 }
 
 bool
-TextEditor::UpdateMetaCharset(nsIDOMDocument* aDocument,
+TextEditor::UpdateMetaCharset(nsIDocument& aDocument,
                               const nsACString& aCharacterSet)
 {
-  MOZ_ASSERT(aDocument);
   // get a list of META tags
-  nsCOMPtr<nsIDOMNodeList> list;
-  nsresult rv = aDocument->GetElementsByTagName(NS_LITERAL_STRING("meta"),
-                                                getter_AddRefs(list));
-  NS_ENSURE_SUCCESS(rv, false);
-  NS_ENSURE_TRUE(list, false);
+  RefPtr<nsContentList> metaList =
+    aDocument.GetElementsByTagName(NS_LITERAL_STRING("meta"));
+  if (!metaList) {
+    return false;
+  }
 
-  nsCOMPtr<nsINodeList> metaList = do_QueryInterface(list);
-
-  uint32_t listLength = 0;
-  metaList->GetLength(&listLength);
+  uint32_t listLength = metaList->Length(true);
 
   for (uint32_t i = 0; i < listLength; ++i) {
     nsCOMPtr<nsIContent> metaNode = metaList->Item(i);
     MOZ_ASSERT(metaNode);
 
     if (!metaNode->IsElement()) {
       continue;
     }
@@ -317,20 +311,21 @@ TextEditor::UpdateMetaCharset(nsIDOMDocu
     if (!FindInReadable(charsetEquals, start, end,
                         nsCaseInsensitiveStringComparator())) {
       continue;
     }
 
     // set attribute to <original prefix> charset=text/html
     RefPtr<Element> metaElement = metaNode->AsElement();
     MOZ_ASSERT(metaElement);
-    rv = EditorBase::SetAttribute(metaElement, nsGkAtoms::content,
-                                  Substring(originalStart, start) +
-                                    charsetEquals +
-                                    NS_ConvertASCIItoUTF16(aCharacterSet));
+    nsresult rv =
+      EditorBase::SetAttribute(metaElement, nsGkAtoms::content,
+                               Substring(originalStart, start) +
+                                 charsetEquals +
+                                 NS_ConvertASCIItoUTF16(aCharacterSet));
     return NS_SUCCEEDED(rv);
   }
   return false;
 }
 
 NS_IMETHODIMP
 TextEditor::InitRules()
 {

--- a/editor/libeditor/TextEditor.h
+++ b/editor/libeditor/TextEditor.h
@@ -222,17 +222,17 @@ protected:
     ePasswordFieldAllowed,
     ePasswordFieldNotAllowed
   };
   bool CanCutOrCopy(PasswordFieldAllowed aPasswordFieldAllowed);
   bool FireClipboardEvent(EventMessage aEventMessage,
                           int32_t aSelectionType,
                           bool* aActionTaken = nullptr);
 
-  bool UpdateMetaCharset(nsIDOMDocument* aDocument,
+  bool UpdateMetaCharset(nsIDocument& aDocument,
                          const nsACString& aCharacterSet);
 
 protected:
   nsCOMPtr<nsIEditRules> mRules;
   int32_t mWrapColumn;
   int32_t mMaxTextLength;
   int32_t mInitTriggerCounter;
   int32_t mNewlineHandling;