--- a/editor/libeditor/EditorBase.cpp
+++ b/editor/libeditor/EditorBase.cpp
@@ -2256,39 +2256,37 @@ EditorBase::CloneAttributes(Element* aDe
   // document
   NS_ENSURE_TRUE(GetRoot(), );
   bool destInBody = GetRoot()->Contains(aDest);
 
   // Clear existing attributes
   RefPtr<nsDOMAttributeMap> destAttributes = aDest->Attributes();
   while (RefPtr<Attr> attr = destAttributes->Item(0)) {
     if (destInBody) {
-      RemoveAttribute(static_cast<nsIDOMElement*>(GetAsDOMNode(aDest)),
-                      attr->NodeName());
+      RemoveAttribute(aDest, attr->NodeInfo()->NameAtom());
     } else {
-      ErrorResult ignored;
-      aDest->RemoveAttribute(attr->NodeName(), ignored);
+      aDest->UnsetAttr(kNameSpaceID_None, attr->NodeInfo()->NameAtom(), true);
     }
   }
 
   // Set just the attributes that the source element has
   RefPtr<nsDOMAttributeMap> sourceAttributes = aSource->Attributes();
   uint32_t sourceCount = sourceAttributes->Length();
   for (uint32_t i = 0; i < sourceCount; i++) {
     RefPtr<Attr> attr = sourceAttributes->Item(i);
     nsAutoString value;
     attr->GetValue(value);
     if (destInBody) {
-      SetAttributeOrEquivalent(static_cast<nsIDOMElement*>(GetAsDOMNode(aDest)),
-                               attr->NodeName(), value, false);
+      SetAttributeOrEquivalent(aDest, attr->NodeInfo()->NameAtom(), value,
+                               false);
     } else {
       // The element is not inserted in the document yet, we don't want to put
       // a transaction on the UndoStack
-      SetAttributeOrEquivalent(static_cast<nsIDOMElement*>(GetAsDOMNode(aDest)),
-                               attr->NodeName(), value, true);
+      SetAttributeOrEquivalent(aDest, attr->NodeInfo()->NameAtom(), value,
+                               true);
     }
   }
 }
 
 NS_IMETHODIMP
 EditorBase::ScrollSelectionIntoView(bool aScrollToAnchor)
 {
   nsCOMPtr<nsISelectionController> selCon;

--- a/editor/libeditor/HTMLEditRules.cpp
+++ b/editor/libeditor/HTMLEditRules.cpp
@@ -3273,25 +3273,25 @@ HTMLEditRules::WillMakeList(Selection* a
         if (!curNode->IsHTMLElement(itemType)) {
           NS_ENSURE_STATE(mHTMLEditor);
           newBlock = mHTMLEditor->ReplaceContainer(curNode->AsElement(),
                                                    itemType);
           NS_ENSURE_STATE(newBlock);
         }
       }
       NS_ENSURE_STATE(mHTMLEditor);
-      nsCOMPtr<nsIDOMElement> curElement = do_QueryInterface(curNode);
-      NS_NAMED_LITERAL_STRING(typestr, "type");
+      nsCOMPtr<Element> curElement = do_QueryInterface(curNode);
       if (aBulletType && !aBulletType->IsEmpty()) {
-        rv = mHTMLEditor->SetAttribute(curElement, typestr, *aBulletType);
+        rv = mHTMLEditor->SetAttribute(curElement, nsGkAtoms::type,
+                                       *aBulletType);
         if (NS_WARN_IF(NS_FAILED(rv))) {
           return rv;
         }
       } else {
-        rv = mHTMLEditor->RemoveAttribute(curElement, typestr);
+        rv = mHTMLEditor->RemoveAttribute(curElement, nsGkAtoms::type);
         if (NS_WARN_IF(NS_FAILED(rv))) {
           return rv;
         }
       }
       continue;
     }
 
     // if we hit a div clear our prevListItem, insert divs contents
@@ -4802,71 +4802,72 @@ HTMLEditRules::AlignInnerBlocks(nsINode&
  */
 nsresult
 HTMLEditRules::AlignBlockContents(nsIDOMNode* aNode,
                                   const nsAString* alignType)
 {
   nsCOMPtr<nsINode> node = do_QueryInterface(aNode);
   NS_ENSURE_TRUE(node && alignType, NS_ERROR_NULL_POINTER);
   nsCOMPtr<nsIContent> firstChild, lastChild;
-  nsCOMPtr<Element> divNode;
 
   bool useCSS = mHTMLEditor->IsCSSEnabled();
 
   NS_ENSURE_STATE(mHTMLEditor);
   firstChild = mHTMLEditor->GetFirstEditableChild(*node);
   NS_ENSURE_STATE(mHTMLEditor);
   lastChild = mHTMLEditor->GetLastEditableChild(*node);
-  NS_NAMED_LITERAL_STRING(attr, "align");
   if (!firstChild) {
     // this cell has no content, nothing to align
   } else if (firstChild == lastChild &&
              firstChild->IsHTMLElement(nsGkAtoms::div)) {
     // the cell already has a div containing all of its content: just
     // act on this div.
-    nsCOMPtr<nsIDOMElement> divElem = do_QueryInterface(firstChild);
+    RefPtr<Element> divElem = firstChild->AsElement();
     if (useCSS) {
       NS_ENSURE_STATE(mHTMLEditor);
-      nsresult rv = mHTMLEditor->SetAttributeOrEquivalent(divElem, attr,
+      nsresult rv = mHTMLEditor->SetAttributeOrEquivalent(divElem,
+                                                          nsGkAtoms::align,
                                                           *alignType, false);
       if (NS_WARN_IF(NS_FAILED(rv))) {
         return rv;
       }
     } else {
       NS_ENSURE_STATE(mHTMLEditor);
-      nsresult rv = mHTMLEditor->SetAttribute(divElem, attr, *alignType);
+      nsresult rv = mHTMLEditor->SetAttribute(divElem, nsGkAtoms::align,
+                                              *alignType);
       if (NS_WARN_IF(NS_FAILED(rv))) {
         return rv;
       }
     }
   } else {
     // else we need to put in a div, set the alignment, and toss in all the children
     NS_ENSURE_STATE(mHTMLEditor);
-    divNode = mHTMLEditor->CreateNode(nsGkAtoms::div, node, 0);
-    NS_ENSURE_STATE(divNode);
+    RefPtr<Element> divElem = mHTMLEditor->CreateNode(nsGkAtoms::div, node, 0);
+    NS_ENSURE_STATE(divElem);
     // set up the alignment on the div
-    nsCOMPtr<nsIDOMElement> divElem = do_QueryInterface(divNode);
     if (useCSS) {
       NS_ENSURE_STATE(mHTMLEditor);
       nsresult rv =
-        mHTMLEditor->SetAttributeOrEquivalent(divElem, attr, *alignType, false);
+        mHTMLEditor->SetAttributeOrEquivalent(divElem, nsGkAtoms::align,
+                                              *alignType, false);
       if (NS_WARN_IF(NS_FAILED(rv))) {
         return rv;
       }
     } else {
       NS_ENSURE_STATE(mHTMLEditor);
-      nsresult rv = mHTMLEditor->SetAttribute(divElem, attr, *alignType);
+      nsresult rv =
+        mHTMLEditor->SetAttribute(divElem, nsGkAtoms::align, *alignType);
       if (NS_WARN_IF(NS_FAILED(rv))) {
         return rv;
       }
     }
     // tuck the children into the end of the active div
-    while (lastChild && (lastChild != divNode)) {
+    while (lastChild && (lastChild != divElem)) {
       NS_ENSURE_STATE(mHTMLEditor);
-      nsresult rv = mHTMLEditor->MoveNode(lastChild, divNode, 0);
+      nsresult rv = mHTMLEditor->MoveNode(lastChild, divElem, 0);
       NS_ENSURE_SUCCESS(rv, rv);
       NS_ENSURE_STATE(mHTMLEditor);
       lastChild = mHTMLEditor->GetLastEditableChild(*node);
     }
   }
   return NS_OK;
 }
 
@@ -6455,19 +6456,19 @@ HTMLEditRules::SplitParagraph(nsIDOMNode
   NS_ENSURE_STATE(mHTMLEditor);
   if (mHTMLEditor->IsVisBreak(aBRNode)) {
     NS_ENSURE_STATE(mHTMLEditor);
     rv = mHTMLEditor->DeleteNode(aBRNode);
     NS_ENSURE_SUCCESS(rv, rv);
   }
 
   // remove ID attribute on the paragraph we just created
-  nsCOMPtr<nsIDOMElement> rightElt = do_QueryInterface(rightPara);
+  RefPtr<Element> rightElt = rightPara->AsElement();
   NS_ENSURE_STATE(mHTMLEditor);
-  rv = mHTMLEditor->RemoveAttribute(rightElt, NS_LITERAL_STRING("id"));
+  rv = mHTMLEditor->RemoveAttribute(rightElt, nsGkAtoms::id);
   NS_ENSURE_SUCCESS(rv, rv);
 
   // check both halves of para to see if we need mozBR
   rv = InsertMozBRIfNeeded(*leftPara);
   NS_ENSURE_SUCCESS(rv, rv);
   rv = InsertMozBRIfNeeded(*rightPara);
   NS_ENSURE_SUCCESS(rv, rv);
 
@@ -8316,28 +8317,28 @@ HTMLEditRules::RemoveAlignment(nsIDOMNod
       // now remove the CENTER container
       NS_ENSURE_STATE(mHTMLEditor);
       nsCOMPtr<Element> childAsElement = do_QueryInterface(child);
       NS_ENSURE_STATE(childAsElement);
       rv = mHTMLEditor->RemoveContainer(childAsElement);
       NS_ENSURE_SUCCESS(rv, rv);
     } else if (isBlock || HTMLEditUtils::IsHR(child)) {
       // the current node is a block element
-      nsCOMPtr<nsIDOMElement> curElem = do_QueryInterface(child);
+      nsCOMPtr<Element> curElem = do_QueryInterface(child);
       if (HTMLEditUtils::SupportsAlignAttr(child)) {
         // remove the ALIGN attribute if this element can have it
         NS_ENSURE_STATE(mHTMLEditor);
-        rv = mHTMLEditor->RemoveAttribute(curElem, NS_LITERAL_STRING("align"));
+        rv = mHTMLEditor->RemoveAttribute(curElem, nsGkAtoms::align);
         NS_ENSURE_SUCCESS(rv, rv);
       }
       if (useCSS) {
         if (HTMLEditUtils::IsTable(child) || HTMLEditUtils::IsHR(child)) {
           NS_ENSURE_STATE(mHTMLEditor);
           rv = mHTMLEditor->SetAttributeOrEquivalent(curElem,
-                                                     NS_LITERAL_STRING("align"),
+                                                     nsGkAtoms::align,
                                                      aAlignType, false);
           if (NS_WARN_IF(NS_FAILED(rv))) {
             return rv;
           }
         } else {
           nsAutoString dummyCssValue;
           NS_ENSURE_STATE(mHTMLEditor);
           rv = mHTMLEditor->mCSSEditUtils->RemoveCSSInlineStyle(
@@ -8447,31 +8448,27 @@ HTMLEditRules::AlignBlock(Element& aElem
   }
 
   NS_ENSURE_STATE(mHTMLEditor);
   RefPtr<HTMLEditor> htmlEditor(mHTMLEditor);
 
   nsresult rv = RemoveAlignment(aElement.AsDOMNode(), aAlignType,
                                 aContentsOnly == ContentsOnly::yes);
   NS_ENSURE_SUCCESS(rv, rv);
-  NS_NAMED_LITERAL_STRING(attr, "align");
   if (htmlEditor->IsCSSEnabled()) {
     // Let's use CSS alignment; we use margin-left and margin-right for tables
     // and text-align for other block-level elements
     rv = htmlEditor->SetAttributeOrEquivalent(
-                       static_cast<nsIDOMElement*>(aElement.AsDOMNode()),
-                       attr, aAlignType, false);
+                       &aElement, nsGkAtoms::align, aAlignType, false);
     NS_ENSURE_SUCCESS(rv, rv);
   } else {
     // HTML case; this code is supposed to be called ONLY if the element
     // supports the align attribute but we'll never know...
     if (HTMLEditUtils::SupportsAlignAttr(aElement.AsDOMNode())) {
-      rv = htmlEditor->SetAttribute(
-                         static_cast<nsIDOMElement*>(aElement.AsDOMNode()),
-                         attr, aAlignType);
+      rv = htmlEditor->SetAttribute(&aElement, nsGkAtoms::align, aAlignType);
       NS_ENSURE_SUCCESS(rv, rv);
     }
   }
   return NS_OK;
 }
 
 nsresult
 HTMLEditRules::ChangeIndentation(Element& aElement,

--- a/editor/libeditor/HTMLEditor.cpp
+++ b/editor/libeditor/HTMLEditor.cpp
@@ -2591,17 +2591,17 @@ HTMLEditor::CreateElementWithDefaults(co
   } else {
     realTagName = tagName;
   }
   // We don't use editor's CreateElement because we don't want to go through
   // the transaction system
 
   // New call to use instead to get proper HTML element, bug 39919
   nsCOMPtr<nsIAtom> realTagAtom = NS_Atomize(realTagName);
-  nsCOMPtr<Element> newElement = CreateHTMLContent(realTagAtom);
+  RefPtr<Element> newElement = CreateHTMLContent(realTagAtom);
   if (!newElement) {
     return nullptr;
   }
 
   // Mark the new element dirty, so it will be formatted
   ErrorResult rv;
   newElement->SetAttribute(NS_LITERAL_STRING("_moz_dirty"), EmptyString(), rv);
 
@@ -2623,18 +2623,17 @@ HTMLEditor::CreateElementWithDefaults(co
                              NS_LITERAL_STRING("1"), rv);
     if (NS_WARN_IF(rv.Failed())) {
       rv.SuppressException();
       return nullptr;
     }
   } else if (tagName.EqualsLiteral("td")) {
     nsresult rv =
       SetAttributeOrEquivalent(
-        static_cast<nsIDOMElement*>(newElement->AsDOMNode()),
-        NS_LITERAL_STRING("valign"), NS_LITERAL_STRING("top"), true);
+        newElement, nsGkAtoms::valign, NS_LITERAL_STRING("top"), true);
     NS_ENSURE_SUCCESS(rv, nullptr);
   }
   // ADD OTHER TAGS HERE
 
   return newElement.forget();
 }
 
 NS_IMETHODIMP

--- a/editor/libeditor/HTMLEditorObjectResizer.cpp
+++ b/editor/libeditor/HTMLEditorObjectResizer.cpp
@@ -905,78 +905,73 @@ HTMLEditor::SetFinalSize(int32_t aX,
 
   int32_t x, y;
   x = left - ((mResizedObjectIsAbsolutelyPositioned) ? mResizedObjectBorderLeft+mResizedObjectMarginLeft : 0);
   y = top - ((mResizedObjectIsAbsolutelyPositioned) ? mResizedObjectBorderTop+mResizedObjectMarginTop : 0);
 
   // we want one transaction only from a user's point of view
   AutoEditBatch batchIt(this);
 
-  NS_NAMED_LITERAL_STRING(widthStr,  "width");
-  NS_NAMED_LITERAL_STRING(heightStr, "height");
-
-  nsCOMPtr<Element> resizedObject = do_QueryInterface(mResizedObject);
-  NS_ENSURE_TRUE(resizedObject, );
   if (mResizedObjectIsAbsolutelyPositioned) {
     if (setHeight) {
-      mCSSEditUtils->SetCSSPropertyPixels(*resizedObject, *nsGkAtoms::top, y);
+      mCSSEditUtils->SetCSSPropertyPixels(*mResizedObject, *nsGkAtoms::top, y);
     }
     if (setWidth) {
-      mCSSEditUtils->SetCSSPropertyPixels(*resizedObject, *nsGkAtoms::left, x);
+      mCSSEditUtils->SetCSSPropertyPixels(*mResizedObject, *nsGkAtoms::left, x);
     }
   }
   if (IsCSSEnabled() || mResizedObjectIsAbsolutelyPositioned) {
     if (setWidth && mResizedObject->HasAttr(kNameSpaceID_None, nsGkAtoms::width)) {
-      RemoveAttribute(static_cast<nsIDOMElement*>(GetAsDOMNode(mResizedObject)), widthStr);
+      RemoveAttribute(mResizedObject, nsGkAtoms::width);
     }
 
     if (setHeight && mResizedObject->HasAttr(kNameSpaceID_None,
                                              nsGkAtoms::height)) {
-      RemoveAttribute(static_cast<nsIDOMElement*>(GetAsDOMNode(mResizedObject)), heightStr);
+      RemoveAttribute(mResizedObject, nsGkAtoms::height);
     }
 
     if (setWidth) {
-      mCSSEditUtils->SetCSSPropertyPixels(*resizedObject, *nsGkAtoms::width,
+      mCSSEditUtils->SetCSSPropertyPixels(*mResizedObject, *nsGkAtoms::width,
                                           width);
     }
     if (setHeight) {
-      mCSSEditUtils->SetCSSPropertyPixels(*resizedObject, *nsGkAtoms::height,
+      mCSSEditUtils->SetCSSPropertyPixels(*mResizedObject, *nsGkAtoms::height,
                                           height);
     }
   } else {
     // we use HTML size and remove all equivalent CSS properties
 
     // we set the CSS width and height to remove it later,
     // triggering an immediate reflow; otherwise, we have problems
     // with asynchronous reflow
     if (setWidth) {
-      mCSSEditUtils->SetCSSPropertyPixels(*resizedObject, *nsGkAtoms::width,
+      mCSSEditUtils->SetCSSPropertyPixels(*mResizedObject, *nsGkAtoms::width,
                                           width);
     }
     if (setHeight) {
-      mCSSEditUtils->SetCSSPropertyPixels(*resizedObject, *nsGkAtoms::height,
+      mCSSEditUtils->SetCSSPropertyPixels(*mResizedObject, *nsGkAtoms::height,
                                           height);
     }
     if (setWidth) {
       nsAutoString w;
       w.AppendInt(width);
-      SetAttribute(static_cast<nsIDOMElement*>(GetAsDOMNode(mResizedObject)), widthStr, w);
+      SetAttribute(mResizedObject, nsGkAtoms::width, w);
     }
     if (setHeight) {
       nsAutoString h;
       h.AppendInt(height);
-      SetAttribute(static_cast<nsIDOMElement*>(GetAsDOMNode(mResizedObject)), heightStr, h);
+      SetAttribute(mResizedObject, nsGkAtoms::height, h);
     }
 
     if (setWidth) {
-      mCSSEditUtils->RemoveCSSProperty(*resizedObject, *nsGkAtoms::width,
+      mCSSEditUtils->RemoveCSSProperty(*mResizedObject, *nsGkAtoms::width,
                                        EmptyString());
     }
     if (setHeight) {
-      mCSSEditUtils->RemoveCSSProperty(*resizedObject, *nsGkAtoms::height,
+      mCSSEditUtils->RemoveCSSProperty(*mResizedObject, *nsGkAtoms::height,
                                        EmptyString());
     }
   }
   // finally notify the listeners if any
   for (auto& listener : mObjectResizeEventListeners) {
     listener->OnEndResizing(static_cast<nsIDOMElement*>(GetAsDOMNode(mResizedObject)),
                             mResizedObjectWidth, mResizedObjectHeight, width,
                             height);

--- a/editor/libeditor/HTMLStyleEditor.cpp
+++ b/editor/libeditor/HTMLStyleEditor.cpp
@@ -726,34 +726,31 @@ HTMLEditor::RemoveStyleInside(nsIContent
        (aProperty == nsGkAtoms::href && HTMLEditUtils::IsLink(&aNode)) ||
        // and for named anchors
        (aProperty == nsGkAtoms::name && HTMLEditUtils::IsNamedAnchor(&aNode)) ||
        // or node is any prop and we asked for that
        (!aProperty && NodeIsProperty(aNode)))) {
     // if we weren't passed an attribute, then we want to
     // remove any matching inlinestyles entirely
     if (!aAttribute || aAttribute->IsEmpty()) {
-      NS_NAMED_LITERAL_STRING(styleAttr, "style");
-      NS_NAMED_LITERAL_STRING(classAttr, "class");
-
       bool hasStyleAttr = aNode.HasAttr(kNameSpaceID_None, nsGkAtoms::style);
       bool hasClassAttr = aNode.HasAttr(kNameSpaceID_None, nsGkAtoms::_class);
       if (aProperty && (hasStyleAttr || hasClassAttr)) {
         // aNode carries inline styles or a class attribute so we can't
         // just remove the element... We need to create above the element
         // a span that will carry those styles or class, then we can delete
         // the node.
-        nsCOMPtr<Element> spanNode =
+        RefPtr<Element> spanNode =
           InsertContainerAbove(&aNode, nsGkAtoms::span);
         NS_ENSURE_STATE(spanNode);
         nsresult rv =
-          CloneAttribute(styleAttr, spanNode->AsDOMNode(), aNode.AsDOMNode());
+          CloneAttribute(nsGkAtoms::style, spanNode, aNode.AsElement());
         NS_ENSURE_SUCCESS(rv, rv);
         rv =
-          CloneAttribute(classAttr, spanNode->AsDOMNode(), aNode.AsDOMNode());
+          CloneAttribute(nsGkAtoms::_class, spanNode, aNode.AsElement());
         NS_ENSURE_SUCCESS(rv, rv);
       }
       nsresult rv = RemoveContainer(&aNode);
       NS_ENSURE_SUCCESS(rv, rv);
     } else {
       // otherwise we just want to eliminate the attribute
       nsCOMPtr<nsIAtom> attribute = NS_Atomize(*aAttribute);
       if (aNode.HasAttr(kNameSpaceID_None, attribute)) {

--- a/editor/libeditor/TextEditRules.cpp
+++ b/editor/libeditor/TextEditRules.cpp
@@ -1420,19 +1420,19 @@ TextEditRules::CreateMozBR(nsIDOMNode* i
   NS_ENSURE_TRUE(inParent, NS_ERROR_NULL_POINTER);
 
   nsCOMPtr<nsIDOMNode> brNode;
   NS_ENSURE_STATE(mTextEditor);
   nsresult rv = mTextEditor->CreateBR(inParent, inOffset, address_of(brNode));
   NS_ENSURE_SUCCESS(rv, rv);
 
   // give it special moz attr
-  nsCOMPtr<nsIDOMElement> brElem = do_QueryInterface(brNode);
+  nsCOMPtr<Element> brElem = do_QueryInterface(brNode);
   if (brElem) {
-    rv = mTextEditor->SetAttribute(brElem, NS_LITERAL_STRING("type"),
+    rv = mTextEditor->SetAttribute(brElem, nsGkAtoms::type,
                                    NS_LITERAL_STRING("_moz"));
     NS_ENSURE_SUCCESS(rv, rv);
   }
 
   if (outBRNode) {
     brNode.forget(outBRNode);
   }
   return NS_OK;

--- a/editor/libeditor/TextEditor.cpp
+++ b/editor/libeditor/TextEditor.cpp
@@ -304,19 +304,19 @@ TextEditor::UpdateMetaCharset(nsIDOMDocu
     originalStart = currentValue.BeginReading(start);
     currentValue.EndReading(end);
     if (!FindInReadable(charsetEquals, start, end,
                         nsCaseInsensitiveStringComparator())) {
       continue;
     }
 
     // set attribute to <original prefix> charset=text/html
-    nsCOMPtr<nsIDOMElement> metaElement = do_QueryInterface(metaNode);
+    RefPtr<Element> metaElement = metaNode->AsElement();
     MOZ_ASSERT(metaElement);
-    rv = EditorBase::SetAttribute(metaElement, NS_LITERAL_STRING("content"),
+    rv = EditorBase::SetAttribute(metaElement, nsGkAtoms::content,
                                   Substring(originalStart, start) +
                                     charsetEquals +
                                     NS_ConvertASCIItoUTF16(aCharacterSet));
     return NS_SUCCEEDED(rv);
   }
   return false;
 }