Merge branch 'redwood' into releaseRELBASE_20200831

12 files changed, 425 insertions, 360 deletions

diff --git a/editor/libeditor/CSSEditUtils.cpp b/editor/libeditor/CSSEditUtils.cpp
index d8146ca65..dfce858a5 100644
--- a/editor/libeditor/CSSEditUtils.cpp
+++ b/editor/libeditor/CSSEditUtils.cpp
@@ -320,6 +320,15 @@ CSSEditUtils::IsCSSEditableProperty(nsINode* aNode,
                                     nsIAtom* aProperty,
                                     const nsAString* aAttribute)
 {
+  nsCOMPtr<nsIAtom> attribute = aAttribute ? NS_Atomize(*aAttribute) : nullptr;
+  return IsCSSEditableProperty(aNode, aProperty, attribute);
+}
+
+bool
+CSSEditUtils::IsCSSEditableProperty(nsINode* aNode,
+                                    nsIAtom* aProperty,
+                                    nsIAtom* aAttribute)
+{
   MOZ_ASSERT(aNode);
 
   nsINode* node = aNode;
@@ -336,13 +345,12 @@ CSSEditUtils::IsCSSEditableProperty(nsINode* aNode,
       nsGkAtoms::u == aProperty ||
       nsGkAtoms::strike == aProperty ||
       (nsGkAtoms::font == aProperty && aAttribute &&
-       (aAttribute->EqualsLiteral("color") ||
-        aAttribute->EqualsLiteral("face")))) {
+       (aAttribute == nsGkAtoms::color || aAttribute == nsGkAtoms::face))) {
     return true;
   }
 
   // ALIGN attribute on elements supporting it
-  if (aAttribute && (aAttribute->EqualsLiteral("align")) &&
+  if (aAttribute == nsGkAtoms::align &&
       node->IsAnyOfHTMLElements(nsGkAtoms::div,
                                 nsGkAtoms::p,
                                 nsGkAtoms::h1,
@@ -365,7 +373,7 @@ CSSEditUtils::IsCSSEditableProperty(nsINode* aNode,
     return true;
   }
 
-  if (aAttribute && (aAttribute->EqualsLiteral("valign")) &&
+  if (aAttribute == nsGkAtoms::valign &&
       node->IsAnyOfHTMLElements(nsGkAtoms::col,
                                 nsGkAtoms::colgroup,
                                 nsGkAtoms::tbody,
@@ -378,59 +386,52 @@ CSSEditUtils::IsCSSEditableProperty(nsINode* aNode,
   }
 
   // attributes TEXT, BACKGROUND and BGCOLOR on BODY
-  if (aAttribute && node->IsHTMLElement(nsGkAtoms::body) &&
-      (aAttribute->EqualsLiteral("text")
-       || aAttribute->EqualsLiteral("background")
-       || aAttribute->EqualsLiteral("bgcolor"))) {
+  if (node->IsHTMLElement(nsGkAtoms::body) &&
+      (aAttribute == nsGkAtoms::text || aAttribute == nsGkAtoms::background ||
+       aAttribute == nsGkAtoms::bgcolor)) {
     return true;
   }
 
   // attribute BGCOLOR on other elements
-  if (aAttribute && aAttribute->EqualsLiteral("bgcolor")) {
+  if (aAttribute == nsGkAtoms::bgcolor) {
     return true;
   }
 
   // attributes HEIGHT, WIDTH and NOWRAP on TD and TH
-  if (aAttribute &&
-      node->IsAnyOfHTMLElements(nsGkAtoms::td, nsGkAtoms::th) &&
-      (aAttribute->EqualsLiteral("height")
-       || aAttribute->EqualsLiteral("width")
-       || aAttribute->EqualsLiteral("nowrap"))) {
+  if (node->IsAnyOfHTMLElements(nsGkAtoms::td, nsGkAtoms::th) &&
+      (aAttribute == nsGkAtoms::height || aAttribute == nsGkAtoms::width ||
+       aAttribute == nsGkAtoms::nowrap)) {
     return true;
   }
 
   // attributes HEIGHT and WIDTH on TABLE
-  if (aAttribute && node->IsHTMLElement(nsGkAtoms::table) &&
-      (aAttribute->EqualsLiteral("height")
-       || aAttribute->EqualsLiteral("width"))) {
+  if (node->IsHTMLElement(nsGkAtoms::table) &&
+      (aAttribute == nsGkAtoms::height || aAttribute == nsGkAtoms::width)) {
     return true;
   }
 
   // attributes SIZE and WIDTH on HR
-  if (aAttribute && node->IsHTMLElement(nsGkAtoms::hr) &&
-      (aAttribute->EqualsLiteral("size")
-       || aAttribute->EqualsLiteral("width"))) {
+  if (node->IsHTMLElement(nsGkAtoms::hr) &&
+      (aAttribute == nsGkAtoms::size || aAttribute == nsGkAtoms::width)) {
     return true;
   }
 
   // attribute TYPE on OL UL LI
-  if (aAttribute &&
-      node->IsAnyOfHTMLElements(nsGkAtoms::ol, nsGkAtoms::ul,
+  if (node->IsAnyOfHTMLElements(nsGkAtoms::ol, nsGkAtoms::ul,
                                 nsGkAtoms::li) &&
-      aAttribute->EqualsLiteral("type")) {
+      aAttribute == nsGkAtoms::type) {
     return true;
   }
 
-  if (aAttribute && node->IsHTMLElement(nsGkAtoms::img) &&
-      (aAttribute->EqualsLiteral("border")
-       || aAttribute->EqualsLiteral("width")
-       || aAttribute->EqualsLiteral("height"))) {
+  if (node->IsHTMLElement(nsGkAtoms::img) &&
+      (aAttribute == nsGkAtoms::border || aAttribute == nsGkAtoms::width ||
+       aAttribute == nsGkAtoms::height)) {
     return true;
   }
 
   // other elements that we can align using CSS even if they
   // can't carry the html ALIGN attribute
-  if (aAttribute && aAttribute->EqualsLiteral("align") &&
+  if (aAttribute == nsGkAtoms::align &&
       node->IsAnyOfHTMLElements(nsGkAtoms::ul,
                                 nsGkAtoms::ol,
                                 nsGkAtoms::dl,
@@ -815,7 +816,7 @@ void
 CSSEditUtils::GenerateCSSDeclarationsFromHTMLStyle(
                 Element* aElement,
                 nsIAtom* aHTMLProperty,
-                const nsAString* aAttribute,
+                nsIAtom* aAttribute,
                 const nsAString* aValue,
                 nsTArray<nsIAtom*>& cssPropertyArray,
                 nsTArray<nsString>& cssValueArray,
@@ -835,21 +836,20 @@ CSSEditUtils::GenerateCSSDeclarationsFromHTMLStyle(
   } else if (nsGkAtoms::tt == aHTMLProperty) {
     equivTable = ttEquivTable;
   } else if (aAttribute) {
-    if (nsGkAtoms::font == aHTMLProperty &&
-        aAttribute->EqualsLiteral("color")) {
+    if (nsGkAtoms::font == aHTMLProperty && aAttribute == nsGkAtoms::color) {
       equivTable = fontColorEquivTable;
     } else if (nsGkAtoms::font == aHTMLProperty &&
-               aAttribute->EqualsLiteral("face")) {
+               aAttribute == nsGkAtoms::face) {
       equivTable = fontFaceEquivTable;
-    } else if (aAttribute->EqualsLiteral("bgcolor")) {
+    } else if (aAttribute == nsGkAtoms::bgcolor) {
       equivTable = bgcolorEquivTable;
-    } else if (aAttribute->EqualsLiteral("background")) {
+    } else if (aAttribute == nsGkAtoms::background) {
       equivTable = backgroundImageEquivTable;
-    } else if (aAttribute->EqualsLiteral("text")) {
+    } else if (aAttribute == nsGkAtoms::text) {
       equivTable = textColorEquivTable;
-    } else if (aAttribute->EqualsLiteral("border")) {
+    } else if (aAttribute == nsGkAtoms::border) {
       equivTable = borderEquivTable;
-    } else if (aAttribute->EqualsLiteral("align")) {
+    } else if (aAttribute == nsGkAtoms::align) {
       if (aElement->IsHTMLElement(nsGkAtoms::table)) {
         equivTable = tableAlignEquivTable;
       } else if (aElement->IsHTMLElement(nsGkAtoms::hr)) {
@@ -860,17 +860,17 @@ CSSEditUtils::GenerateCSSDeclarationsFromHTMLStyle(
       } else {
         equivTable = textAlignEquivTable;
       }
-    } else if (aAttribute->EqualsLiteral("valign")) {
+    } else if (aAttribute == nsGkAtoms::valign) {
       equivTable = verticalAlignEquivTable;
-    } else if (aAttribute->EqualsLiteral("nowrap")) {
+    } else if (aAttribute == nsGkAtoms::nowrap) {
       equivTable = nowrapEquivTable;
-    } else if (aAttribute->EqualsLiteral("width")) {
+    } else if (aAttribute == nsGkAtoms::width) {
       equivTable = widthEquivTable;
-    } else if (aAttribute->EqualsLiteral("height") ||
+    } else if (aAttribute == nsGkAtoms::height ||
                (aElement->IsHTMLElement(nsGkAtoms::hr) &&
-                aAttribute->EqualsLiteral("size"))) {
+                aAttribute == nsGkAtoms::size)) {
       equivTable = heightEquivTable;
-    } else if (aAttribute->EqualsLiteral("type") &&
+    } else if (aAttribute == nsGkAtoms::type &&
                aElement->IsAnyOfHTMLElements(nsGkAtoms::ol,
                                              nsGkAtoms::ul,
                                              nsGkAtoms::li)) {
@@ -887,40 +887,46 @@ CSSEditUtils::GenerateCSSDeclarationsFromHTMLStyle(
 // aValue for the node, and return in aCount the number of CSS properties set
 // by the call.  The Element version returns aCount instead.
 int32_t
-CSSEditUtils::SetCSSEquivalentToHTMLStyle(Element* aElement,
+CSSEditUtils::SetCSSEquivalentToHTMLStyle(nsIDOMNode* aNode,
                                           nsIAtom* aProperty,
                                           const nsAString* aAttribute,
                                           const nsAString* aValue,
                                           bool aSuppressTransaction)
 {
-  MOZ_ASSERT(aElement && aProperty);
   MOZ_ASSERT_IF(aAttribute, aValue);
-  int32_t count;
   // This can only fail if SetCSSProperty fails, which should only happen if
   // something is pretty badly wrong.  In this case we assert so that hopefully
   // someone will notice, but there's nothing more sensible to do than just
   // return the count and carry on.
-  nsresult rv = SetCSSEquivalentToHTMLStyle(aElement->AsDOMNode(),
-                                            aProperty, aAttribute,
-                                            aValue, &count,
-                                            aSuppressTransaction);
-  NS_ASSERTION(NS_SUCCEEDED(rv), "SetCSSEquivalentToHTMLStyle failed");
-  NS_ENSURE_SUCCESS(rv, count);
-  return count;
+  nsCOMPtr<Element> element = do_QueryInterface(aNode);
+  return SetCSSEquivalentToHTMLStyle(element,
+                                     aProperty, aAttribute,
+                                     aValue, aSuppressTransaction);
 }
 
-nsresult
-CSSEditUtils::SetCSSEquivalentToHTMLStyle(nsIDOMNode* aNode,
+int32_t
+CSSEditUtils::SetCSSEquivalentToHTMLStyle(Element* aElement,
                                           nsIAtom* aHTMLProperty,
                                           const nsAString* aAttribute,
                                           const nsAString* aValue,
-                                          int32_t* aCount,
                                           bool aSuppressTransaction)
 {
-  nsCOMPtr<Element> element = do_QueryInterface(aNode);
-  *aCount = 0;
-  if (!element || !IsCSSEditableProperty(element, aHTMLProperty, aAttribute)) {
-    return NS_OK;
+  nsCOMPtr<nsIAtom> attribute = aAttribute ? NS_Atomize(*aAttribute) : nullptr;
+  return SetCSSEquivalentToHTMLStyle(aElement, aHTMLProperty, attribute,
+                                     aValue, aSuppressTransaction);
+}
+
+int32_t
+CSSEditUtils::SetCSSEquivalentToHTMLStyle(Element* aElement,
+                                          nsIAtom* aHTMLProperty,
+                                          nsIAtom* aAttribute,
+                                          const nsAString* aValue,
+                                          bool aSuppressTransaction)
+{
+  MOZ_ASSERT(aElement);
+
+  if (!IsCSSEditableProperty(aElement, aHTMLProperty, aAttribute)) {
+    return 0;
   }
 
   // we can apply the styles only if the node is an element and if we have
@@ -929,18 +935,20 @@ CSSEditUtils::SetCSSEquivalentToHTMLStyle(nsIDOMNode* aNode,
   // Find the CSS equivalence to the HTML style
   nsTArray<nsIAtom*> cssPropertyArray;
   nsTArray<nsString> cssValueArray;
-  GenerateCSSDeclarationsFromHTMLStyle(element, aHTMLProperty, aAttribute,
+  GenerateCSSDeclarationsFromHTMLStyle(aElement, aHTMLProperty, aAttribute,
                                        aValue, cssPropertyArray, cssValueArray,
                                        false);
 
   // set the individual CSS inline styles
-  *aCount = cssPropertyArray.Length();
-  for (int32_t index = 0; index < *aCount; index++) {
-    nsresult rv = SetCSSProperty(*element, *cssPropertyArray[index],
+  size_t count = cssPropertyArray.Length();
+  for (size_t index = 0; index < count; index++) {
+    nsresult rv = SetCSSProperty(*aElement, *cssPropertyArray[index],
                                  cssValueArray[index], aSuppressTransaction);
-    NS_ENSURE_SUCCESS(rv, rv);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return 0;
+    }
   }
-  return NS_OK;
+  return count;
 }
 
 // Remove from aNode the CSS inline style equivalent to HTMLProperty/aAttribute/aValue for the node
@@ -952,20 +960,22 @@ CSSEditUtils::RemoveCSSEquivalentToHTMLStyle(nsIDOMNode* aNode,
                                              bool aSuppressTransaction)
 {
   nsCOMPtr<Element> element = do_QueryInterface(aNode);
-  NS_ENSURE_TRUE(element, NS_OK);
+  nsCOMPtr<nsIAtom> attribute = aAttribute ? NS_Atomize(*aAttribute) : nullptr;
 
-  return RemoveCSSEquivalentToHTMLStyle(element, aHTMLProperty, aAttribute,
+  return RemoveCSSEquivalentToHTMLStyle(element, aHTMLProperty, attribute,
                                         aValue, aSuppressTransaction);
 }
 
 nsresult
 CSSEditUtils::RemoveCSSEquivalentToHTMLStyle(Element* aElement,
                                              nsIAtom* aHTMLProperty,
-                                             const nsAString* aAttribute,
+                                             nsIAtom* aAttribute,
                                              const nsAString* aValue,
                                              bool aSuppressTransaction)
 {
-  MOZ_ASSERT(aElement);
+  if (NS_WARN_IF(!aElement)) {
+    return NS_OK;
+  }
 
   if (!IsCSSEditableProperty(aElement, aHTMLProperty, aAttribute)) {
     return NS_OK;
@@ -1000,7 +1010,7 @@ CSSEditUtils::RemoveCSSEquivalentToHTMLStyle(Element* aElement,
 nsresult
 CSSEditUtils::GetCSSEquivalentToHTMLInlineStyleSet(nsINode* aNode,
                                                    nsIAtom* aHTMLProperty,
-                                                   const nsAString* aAttribute,
+                                                   nsIAtom* aAttribute,
                                                    nsAString& aValueString,
                                                    StyleType aStyleType)
 {
@@ -1017,7 +1027,8 @@ CSSEditUtils::GetCSSEquivalentToHTMLInlineStyleSet(nsINode* aNode,
   nsTArray<nsString> cssValueArray;
   // get the CSS equivalence with last param true indicating we want only the
   // "gettable" properties
-  GenerateCSSDeclarationsFromHTMLStyle(theElement, aHTMLProperty, aAttribute, nullptr,
+  GenerateCSSDeclarationsFromHTMLStyle(theElement, aHTMLProperty, aAttribute,
+                                       nullptr,
                                        cssPropertyArray, cssValueArray, true);
   int32_t count = cssPropertyArray.Length();
   for (int32_t index = 0; index < count; index++) {
@@ -1063,48 +1074,58 @@ CSSEditUtils::IsCSSEquivalentToHTMLInlineStyleSet(nsINode* aNode,
                                                   StyleType aStyleType)
 {
   MOZ_ASSERT(aNode && aProperty);
-  bool isSet;
-  nsresult rv = IsCSSEquivalentToHTMLInlineStyleSet(aNode->AsDOMNode(),
-                                                    aProperty, aAttribute,
-                                                    isSet, aValue, aStyleType);
-  NS_ENSURE_SUCCESS(rv, false);
-  return isSet;
+  nsCOMPtr<nsIAtom> attribute = aAttribute ? NS_Atomize(*aAttribute) : nullptr;
+  return IsCSSEquivalentToHTMLInlineStyleSet(aNode,
+                                             aProperty, attribute,
+                                             aValue, aStyleType);
 }
 
-nsresult
+bool
+CSSEditUtils::IsCSSEquivalentToHTMLInlineStyleSet(nsIDOMNode* aNode,
+                                                  nsIAtom* aProperty,
+                                                  const nsAString* aAttribute,
+                                                  nsAString& aValue,
+                                                  StyleType aStyleType)
+{
+  MOZ_ASSERT(aNode && aProperty);
+  nsCOMPtr<nsINode> node = do_QueryInterface(aNode);
+  nsCOMPtr<nsIAtom> attribute = aAttribute ? NS_Atomize(*aAttribute) : nullptr;
+  return IsCSSEquivalentToHTMLInlineStyleSet(node, aProperty, attribute,
+                                             aValue, aStyleType);
+}
+
+bool
 CSSEditUtils::IsCSSEquivalentToHTMLInlineStyleSet(
-                nsIDOMNode* aNode,
+                nsINode* aNode,
                 nsIAtom* aHTMLProperty,
-                const nsAString* aHTMLAttribute,
-                bool& aIsSet,
+                nsIAtom* aHTMLAttribute,
                 nsAString& valueString,
                 StyleType aStyleType)
 {
-  NS_ENSURE_TRUE(aNode, NS_ERROR_NULL_POINTER);
+  NS_ENSURE_TRUE(aNode, false);
 
   nsAutoString htmlValueString(valueString);
-  aIsSet = false;
-  nsCOMPtr<nsINode> node = do_QueryInterface(aNode);
+  bool isSet = false;
   do {
     valueString.Assign(htmlValueString);
     // get the value of the CSS equivalent styles
     nsresult rv =
-      GetCSSEquivalentToHTMLInlineStyleSet(node, aHTMLProperty, aHTMLAttribute,
+      GetCSSEquivalentToHTMLInlineStyleSet(aNode, aHTMLProperty, aHTMLAttribute,
                                            valueString, aStyleType);
-    NS_ENSURE_SUCCESS(rv, rv);
+    NS_ENSURE_SUCCESS(rv, false);
 
     // early way out if we can
     if (valueString.IsEmpty()) {
-      return NS_OK;
+      return isSet;
     }
 
     if (nsGkAtoms::b == aHTMLProperty) {
       if (valueString.EqualsLiteral("bold")) {
-        aIsSet = true;
+        isSet = true;
       } else if (valueString.EqualsLiteral("normal")) {
-        aIsSet = false;
+        isSet = false;
       } else if (valueString.EqualsLiteral("bolder")) {
-        aIsSet = true;
+        isSet = true;
         valueString.AssignLiteral("bold");
       } else {
         int32_t weight = 0;
@@ -1112,32 +1133,31 @@ CSSEditUtils::IsCSSEquivalentToHTMLInlineStyleSet(
         nsAutoString value(valueString);
         weight = value.ToInteger(&errorCode);
         if (400 < weight) {
-          aIsSet = true;
+          isSet = true;
           valueString.AssignLiteral("bold");
         } else {
-          aIsSet = false;
+          isSet = false;
           valueString.AssignLiteral("normal");
         }
       }
     } else if (nsGkAtoms::i == aHTMLProperty) {
       if (valueString.EqualsLiteral("italic") ||
           valueString.EqualsLiteral("oblique")) {
-        aIsSet = true;
+        isSet = true;
       }
     } else if (nsGkAtoms::u == aHTMLProperty) {
       nsAutoString val;
       val.AssignLiteral("underline");
-      aIsSet = ChangeStyleTransaction::ValueIncludes(valueString, val);
+      isSet = ChangeStyleTransaction::ValueIncludes(valueString, val);
     } else if (nsGkAtoms::strike == aHTMLProperty) {
       nsAutoString val;
       val.AssignLiteral("line-through");
-      aIsSet = ChangeStyleTransaction::ValueIncludes(valueString, val);
-    } else if (aHTMLAttribute &&
-               ((nsGkAtoms::font == aHTMLProperty &&
-                 aHTMLAttribute->EqualsLiteral("color")) ||
-                aHTMLAttribute->EqualsLiteral("bgcolor"))) {
+      isSet = ChangeStyleTransaction::ValueIncludes(valueString, val);
+    } else if ((nsGkAtoms::font == aHTMLProperty &&
+                aHTMLAttribute == nsGkAtoms::color) ||
+               aHTMLAttribute == nsGkAtoms::bgcolor) {
       if (htmlValueString.IsEmpty()) {
-        aIsSet = true;
+        isSet = true;
       } else {
         nscolor rgba;
         nsAutoString subStr;
@@ -1171,54 +1191,53 @@ CSSEditUtils::IsCSSEquivalentToHTMLInlineStyleSet(
             htmlColor.Append(char16_t(')'));
           }
 
-          aIsSet = htmlColor.Equals(valueString,
-                                    nsCaseInsensitiveStringComparator());
+          isSet = htmlColor.Equals(valueString,
+                                   nsCaseInsensitiveStringComparator());
         } else {
-          aIsSet = htmlValueString.Equals(valueString,
-                                    nsCaseInsensitiveStringComparator());
+          isSet = htmlValueString.Equals(valueString,
+                                         nsCaseInsensitiveStringComparator());
         }
       }
     } else if (nsGkAtoms::tt == aHTMLProperty) {
-      aIsSet = StringBeginsWith(valueString, NS_LITERAL_STRING("monospace"));
+      isSet = StringBeginsWith(valueString, NS_LITERAL_STRING("monospace"));
     } else if (nsGkAtoms::font == aHTMLProperty && aHTMLAttribute &&
-               aHTMLAttribute->EqualsLiteral("face")) {
+               aHTMLAttribute == nsGkAtoms::face) {
       if (!htmlValueString.IsEmpty()) {
         const char16_t commaSpace[] = { char16_t(','), char16_t(' '), 0 };
         const char16_t comma[] = { char16_t(','), 0 };
         htmlValueString.ReplaceSubstring(commaSpace, comma);
         nsAutoString valueStringNorm(valueString);
         valueStringNorm.ReplaceSubstring(commaSpace, comma);
-        aIsSet = htmlValueString.Equals(valueStringNorm,
-                                        nsCaseInsensitiveStringComparator());
+        isSet = htmlValueString.Equals(valueStringNorm,
+                                       nsCaseInsensitiveStringComparator());
       } else {
-        aIsSet = true;
+        isSet = true;
       }
-      return NS_OK;
-    } else if (aHTMLAttribute && aHTMLAttribute->EqualsLiteral("align")) {
-      aIsSet = true;
+      return isSet;
+    } else if (aHTMLAttribute == nsGkAtoms::align) {
+      isSet = true;
     } else {
-      aIsSet = false;
-      return NS_OK;
+      return false;
     }
 
     if (!htmlValueString.IsEmpty() &&
         htmlValueString.Equals(valueString,
                                nsCaseInsensitiveStringComparator())) {
-      aIsSet = true;
+      isSet = true;
     }
 
     if (htmlValueString.EqualsLiteral("-moz-editor-invert-value")) {
-      aIsSet = !aIsSet;
+      isSet = !isSet;
     }
 
     if (nsGkAtoms::u == aHTMLProperty || nsGkAtoms::strike == aHTMLProperty) {
       // unfortunately, the value of the text-decoration property is not inherited.
       // that means that we have to look at ancestors of node to see if they are underlined
-      node = node->GetParentElement();  // set to null if it's not a dom element
+      aNode = aNode->GetParentElement(); // set to null if it's not a dom element
     }
   } while ((nsGkAtoms::u == aHTMLProperty ||
-            nsGkAtoms::strike == aHTMLProperty) && !aIsSet && node);
-  return NS_OK;
+            nsGkAtoms::strike == aHTMLProperty) && !isSet && aNode);
+  return isSet;
 }
 
 void
diff --git a/editor/libeditor/CSSEditUtils.h b/editor/libeditor/CSSEditUtils.h
index 0b9a12952..5129ab88d 100644
--- a/editor/libeditor/CSSEditUtils.h
+++ b/editor/libeditor/CSSEditUtils.h
@@ -90,6 +90,8 @@ public:
    */
   bool IsCSSEditableProperty(nsINode* aNode, nsIAtom* aProperty,
                              const nsAString* aAttribute);
+  bool IsCSSEditableProperty(nsINode* aNode, nsIAtom* aProperty,
+                             nsIAtom* aAttribute);
 
   /**
    * Adds/remove a CSS declaration to the STYLE atrribute carried by a given
@@ -188,14 +190,14 @@ public:
    *
    * @param aNode          [IN] A DOM node.
    * @param aHTMLProperty  [IN] An atom containing an HTML property.
-   * @param aAttribute     [IN] A pointer to an attribute name or nullptr if
+   * @param aAttribute     [IN] An atom of attribute name or nullptr if
    *                            irrelevant.
    * @param aValueString   [OUT] The list of CSS values.
    * @param aStyleType     [IN] eSpecified or eComputed.
    */
   nsresult GetCSSEquivalentToHTMLInlineStyleSet(nsINode* aNode,
                                                 nsIAtom* aHTMLProperty,
-                                                const nsAString* aAttribute,
+                                                nsIAtom* aAttribute,
                                                 nsAString& aValueString,
                                                 StyleType aStyleType);
 
@@ -205,18 +207,22 @@ public:
    *
    * @param aNode          [IN] A DOM node.
    * @param aHTMLProperty  [IN] An atom containing an HTML property.
-   * @param aAttribute     [IN] A pointer to an attribute name or nullptr if
-   *                            irrelevant.
-   * @param aIsSet         [OUT] A boolean being true if the css properties are
-   *                             set.
+   * @param aAttribute     [IN] A pointer/atom to an attribute name or nullptr
+   *                            if irrelevant.
    * @param aValueString   [IN/OUT] The attribute value (in) the list of CSS
    *                                values (out).
    * @param aStyleType     [IN] eSpecified or eComputed.
-   *
-   * The nsIContent variant returns aIsSet instead of using an out parameter.
+   * @return               A boolean being true if the css properties are
+   *                       set.
    */
   bool IsCSSEquivalentToHTMLInlineStyleSet(nsINode* aContent,
                                            nsIAtom* aProperty,
+                                           nsIAtom* aAttribute,
+                                           nsAString& aValue,
+                                           StyleType aStyleType);
+
+  bool IsCSSEquivalentToHTMLInlineStyleSet(nsINode* aContent,
+                                           nsIAtom* aProperty,
                                            const nsAString* aAttribute,
                                            const nsAString& aValue,
                                            StyleType aStyleType);
@@ -227,12 +233,11 @@ public:
                                            nsAString& aValue,
                                            StyleType aStyleType);
 
-  nsresult IsCSSEquivalentToHTMLInlineStyleSet(nsIDOMNode* aNode,
-                                               nsIAtom* aHTMLProperty,
-                                               const nsAString* aAttribute,
-                                               bool& aIsSet,
-                                               nsAString& aValueString,
-                                               StyleType aStyleType);
+  bool IsCSSEquivalentToHTMLInlineStyleSet(nsIDOMNode* aNode,
+                                           nsIAtom* aProperty,
+                                           const nsAString* aAttribute,
+                                           nsAString& aValue,
+                                           StyleType aStyleType);
 
   /**
    * Adds to the node the CSS inline styles equivalent to the HTML style
@@ -240,27 +245,29 @@ public:
    *
    * @param aNode          [IN] A DOM node.
    * @param aHTMLProperty  [IN] An atom containing an HTML property.
-   * @param aAttribute     [IN] A pointer to an attribute name or nullptr if
-   *                            irrelevant.
+   * @param aAttribute     [IN] A pointer/atom to an attribute name or nullptr
+   *                            if irrelevant.
    * @param aValue         [IN] The attribute value.
-   * @param aCount         [OUT] The number of CSS properties set by the call.
    * @param aSuppressTransaction [IN] A boolean indicating, when true,
    *                                  that no transaction should be recorded.
    *
-   * aCount is returned by the dom::Element variant instead of being an out
-   * parameter.
+   * @return               The number of CSS properties set by the call.
    */
   int32_t SetCSSEquivalentToHTMLStyle(dom::Element* aElement,
                                       nsIAtom* aProperty,
+                                      nsIAtom* aAttribute,
+                                      const nsAString* aValue,
+                                      bool aSuppressTransaction);
+  int32_t SetCSSEquivalentToHTMLStyle(dom::Element* aElement,
+                                      nsIAtom* aProperty,
+                                      const nsAString* aAttribute,
+                                      const nsAString* aValue,
+                                      bool aSuppressTransaction);
+  int32_t SetCSSEquivalentToHTMLStyle(nsIDOMNode* aNode,
+                                      nsIAtom* aHTMLProperty,
                                       const nsAString* aAttribute,
                                       const nsAString* aValue,
                                       bool aSuppressTransaction);
-  nsresult SetCSSEquivalentToHTMLStyle(nsIDOMNode* aNode,
-                                       nsIAtom* aHTMLProperty,
-                                       const nsAString* aAttribute,
-                                       const nsAString* aValue,
-                                       int32_t* aCount,
-                                       bool aSuppressTransaction);
 
   /**
    * Removes from the node the CSS inline styles equivalent to the HTML style.
@@ -284,7 +291,7 @@ public:
    *
    * @param aElement       [IN] A DOM Element (must not be null).
    * @param aHTMLProperty  [IN] An atom containing an HTML property.
-   * @param aAttribute     [IN] A pointer to an attribute name or nullptr if
+   * @param aAttribute     [IN] An atom to an attribute name or nullptr if
    *                            irrelevant.
    * @param aValue         [IN] The attribute value.
    * @param aSuppressTransaction [IN] A boolean indicating, when true,
@@ -292,7 +299,7 @@ public:
    */
   nsresult RemoveCSSEquivalentToHTMLStyle(dom::Element* aElement,
                                           nsIAtom* aHTMLProperty,
-                                          const nsAString* aAttribute,
+                                          nsIAtom* aAttribute,
                                           const nsAString* aValue,
                                           bool aSuppressTransaction);
 
@@ -409,7 +416,7 @@ private:
    *
    * @param aNode              [IN] The DOM node.
    * @param aHTMLProperty      [IN] An atom containing an HTML property.
-   * @param aAttribute         [IN] A pointer to an attribute name or nullptr
+   * @param aAttribute         [IN] An atom to an attribute name or nullptr
    *                                if irrelevant
    * @param aValue             [IN] The attribute value.
    * @param aPropertyArray     [OUT] The array of CSS properties.
@@ -422,7 +429,7 @@ private:
    */
   void GenerateCSSDeclarationsFromHTMLStyle(dom::Element* aNode,
                                             nsIAtom* aHTMLProperty,
-                                            const nsAString* aAttribute,
+                                            nsIAtom* aAttribute,
                                             const nsAString* aValue,
                                             nsTArray<nsIAtom*>& aPropertyArray,
                                             nsTArray<nsString>& aValueArray,
diff --git a/editor/libeditor/EditorBase.cpp b/editor/libeditor/EditorBase.cpp
index f7988cd1a..0cd3f01b7 100644
--- a/editor/libeditor/EditorBase.cpp
+++ b/editor/libeditor/EditorBase.cpp
@@ -1229,12 +1229,23 @@ EditorBase::SetAttribute(nsIDOMElement* aElement,
                          const nsAString& aAttribute,
                          const nsAString& aValue)
 {
+  if (NS_WARN_IF(aAttribute.IsEmpty())) {
+    return NS_ERROR_FAILURE;
+  }
   nsCOMPtr<Element> element = do_QueryInterface(aElement);
   NS_ENSURE_TRUE(element, NS_ERROR_NULL_POINTER);
   nsCOMPtr<nsIAtom> attribute = NS_Atomize(aAttribute);
 
+  return SetAttribute(element, attribute, aValue);
+}
+
+nsresult
+EditorBase::SetAttribute(Element* aElement,
+                         nsIAtom* aAttribute,
+                         const nsAString& aValue)
+{
   RefPtr<ChangeAttributeTransaction> transaction =
-    CreateTxnForSetAttribute(*element, *attribute, aValue);
+    CreateTxnForSetAttribute(*aElement, *aAttribute, aValue);
   return DoTransaction(transaction);
 }
 
@@ -1263,12 +1274,22 @@ NS_IMETHODIMP
 EditorBase::RemoveAttribute(nsIDOMElement* aElement,
                             const nsAString& aAttribute)
 {
+  if (NS_WARN_IF(aAttribute.IsEmpty())) {
+    return NS_ERROR_FAILURE;
+  }
   nsCOMPtr<Element> element = do_QueryInterface(aElement);
   NS_ENSURE_TRUE(element, NS_ERROR_NULL_POINTER);
   nsCOMPtr<nsIAtom> attribute = NS_Atomize(aAttribute);
 
+  return RemoveAttribute(element, attribute);
+}
+
+nsresult
+EditorBase::RemoveAttribute(Element* aElement,
+                            nsIAtom* aAttribute)
+{
   RefPtr<ChangeAttributeTransaction> transaction =
-    CreateTxnForRemoveAttribute(*element, *attribute);
+    CreateTxnForRemoveAttribute(*aElement, *aAttribute);
   return DoTransaction(transaction);
 }
 
@@ -2208,25 +2229,28 @@ EditorBase::CloneAttribute(const nsAString& aAttribute,
                            nsIDOMNode* aSourceNode)
 {
   NS_ENSURE_TRUE(aDestNode && aSourceNode, NS_ERROR_NULL_POINTER);
+  if (NS_WARN_IF(aAttribute.IsEmpty())) {
+    return NS_ERROR_FAILURE;
+  }
 
-  nsCOMPtr<nsIDOMElement> destElement = do_QueryInterface(aDestNode);
-  nsCOMPtr<nsIDOMElement> sourceElement = do_QueryInterface(aSourceNode);
+  nsCOMPtr<Element> destElement = do_QueryInterface(aDestNode);
+  nsCOMPtr<Element> sourceElement = do_QueryInterface(aSourceNode);
   NS_ENSURE_TRUE(destElement && sourceElement, NS_ERROR_NO_INTERFACE);
 
+  nsCOMPtr<nsIAtom> attribute = NS_Atomize(aAttribute);
+  return CloneAttribute(attribute, destElement, sourceElement);
+}
+
+nsresult
+EditorBase::CloneAttribute(nsIAtom* aAttribute,
+                           Element* aDestElement,
+                           Element* aSourceElement)
+{
   nsAutoString attrValue;
-  bool isAttrSet;
-  nsresult rv = GetAttributeValue(sourceElement,
-                                  aAttribute,
-                                  attrValue,
-                                  &isAttrSet);
-  NS_ENSURE_SUCCESS(rv, rv);
-  if (isAttrSet) {
-    rv = SetAttribute(destElement, aAttribute, attrValue);
-  } else {
-    rv = RemoveAttribute(destElement, aAttribute);
+  if (aSourceElement->GetAttr(kNameSpaceID_None, aAttribute, attrValue)) {
+    return SetAttribute(aDestElement, aAttribute, attrValue);
   }
-
-  return rv;
+  return RemoveAttribute(aDestElement, aAttribute);
 }
 
 /**
@@ -2265,11 +2289,9 @@ EditorBase::CloneAttributes(Element* aDest,
   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);
     }
   }
 
@@ -2281,13 +2303,13 @@ EditorBase::CloneAttributes(Element* aDest,
     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);
     }
   }
 }
@@ -4618,21 +4640,32 @@ EditorBase::CreateHTMLContent(nsIAtom* aTag)
                          kNameSpaceID_XHTML);
 }
 
-nsresult
+NS_IMETHODIMP
 EditorBase::SetAttributeOrEquivalent(nsIDOMElement* aElement,
                                      const nsAString& aAttribute,
                                      const nsAString& aValue,
                                      bool aSuppressTransaction)
 {
-  return SetAttribute(aElement, aAttribute, aValue);
+  nsCOMPtr<Element> element = do_QueryInterface(aElement);
+  if (NS_WARN_IF(!element)) {
+    return NS_ERROR_NULL_POINTER;
+  }
+  nsCOMPtr<nsIAtom> attribute = NS_Atomize(aAttribute);
+  return SetAttributeOrEquivalent(element, attribute, aValue,
+                                  aSuppressTransaction);
 }
 
-nsresult
+NS_IMETHODIMP
 EditorBase::RemoveAttributeOrEquivalent(nsIDOMElement* aElement,
                                         const nsAString& aAttribute,
                                         bool aSuppressTransaction)
 {
-  return RemoveAttribute(aElement, aAttribute);
+  nsCOMPtr<Element> element = do_QueryInterface(aElement);
+  if (NS_WARN_IF(!element)) {
+    return NS_ERROR_NULL_POINTER;
+  }
+  nsCOMPtr<nsIAtom> attribute = NS_Atomize(aAttribute);
+  return RemoveAttributeOrEquivalent(element, attribute, aSuppressTransaction);
 }
 
 nsresult
diff --git a/editor/libeditor/EditorBase.h b/editor/libeditor/EditorBase.h
index dbd00771e..e537c77cf 100644
--- a/editor/libeditor/EditorBase.h
+++ b/editor/libeditor/EditorBase.h
@@ -236,6 +236,19 @@ public:
   nsresult JoinNodes(nsINode& aLeftNode, nsINode& aRightNode);
   nsresult MoveNode(nsIContent* aNode, nsINode* aParent, int32_t aOffset);
 
+  nsresult CloneAttribute(nsIAtom* aAttribute, Element* aDestElement,
+                          Element* aSourceElement);
+  nsresult RemoveAttribute(Element* aElement, nsIAtom* aAttribute);
+  virtual nsresult RemoveAttributeOrEquivalent(Element* aElement,
+                                               nsIAtom* aAttribute,
+                                               bool aSuppressTransaction) = 0;
+  nsresult SetAttribute(Element* aElement, nsIAtom* aAttribute,
+                        const nsAString& aValue);
+  virtual nsresult SetAttributeOrEquivalent(Element* aElement,
+                                            nsIAtom* aAttribute,
+                                            const nsAString& aValue,
+                                            bool aSuppressTransaction) = 0;
+
   /**
    * Method to replace certain CreateElementNS() calls.
    *
diff --git a/editor/libeditor/HTMLEditRules.cpp b/editor/libeditor/HTMLEditRules.cpp
index d3cbb8775..dfc327a2c 100644
--- a/editor/libeditor/HTMLEditRules.cpp
+++ b/editor/libeditor/HTMLEditRules.cpp
@@ -839,19 +839,18 @@ HTMLEditRules::GetAlignment(bool* aMixed,
 
   NS_ENSURE_TRUE(nodeToExamine, NS_ERROR_NULL_POINTER);
 
-  NS_NAMED_LITERAL_STRING(typeAttrName, "align");
   nsCOMPtr<Element> blockParent = htmlEditor->GetBlock(*nodeToExamine);
 
   NS_ENSURE_TRUE(blockParent, NS_ERROR_FAILURE);
 
   if (htmlEditor->IsCSSEnabled() &&
       htmlEditor->mCSSEditUtils->IsCSSEditableProperty(blockParent, nullptr,
-                                                        &typeAttrName)) {
+                                                       nsGkAtoms::align)) {
     // We are in CSS mode and we know how to align this element with CSS
     nsAutoString value;
     // Let's get the value(s) of text-align or margin-left/margin-right
     htmlEditor->mCSSEditUtils->GetCSSEquivalentToHTMLInlineStyleSet(
-        blockParent, nullptr, &typeAttrName, value, CSSEditUtils::eComputed);
+        blockParent, nullptr, nsGkAtoms::align, value, CSSEditUtils::eComputed);
     if (value.EqualsLiteral("center") ||
         value.EqualsLiteral("-moz-center") ||
         value.EqualsLiteral("auto auto")) {
@@ -1510,10 +1509,11 @@ HTMLEditRules::WillInsertBreak(Selection& aSelection,
   nsCOMPtr<Element> blockParent = htmlEditor->GetBlock(node);
   NS_ENSURE_TRUE(blockParent, NS_ERROR_FAILURE);
 
-  // If the active editing host is an inline element, or if the active editing
-  // host is the block parent itself, just append a br.
+  // When there is an active editing host (the <body> if it's in designMode)
+  // and a block which becomes the parent of line breaker is in it, do the
+  // standard thing.
   nsCOMPtr<Element> host = htmlEditor->GetActiveEditingHost();
-  if (!EditorUtils::IsDescendantOf(blockParent, host)) {
+  if (host && !EditorUtils::IsDescendantOf(blockParent, host)) {
     nsresult rv = StandardBreakImpl(node, offset, aSelection);
     NS_ENSURE_SUCCESS(rv, rv);
     *aHandled = true;
@@ -3303,15 +3303,15 @@ HTMLEditRules::WillMakeList(Selection* aSelection,
         }
       }
       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;
         }
@@ -4755,7 +4755,7 @@ HTMLEditRules::WillAlign(Selection& aSelection,
       NS_ENSURE_SUCCESS(rv, rv);
       if (useCSS) {
         htmlEditor->mCSSEditUtils->SetCSSEquivalentToHTMLStyle(
-            curNode->AsElement(), nullptr, &NS_LITERAL_STRING("align"),
+            curNode->AsElement(), nullptr, nsGkAtoms::align,
             &aAlignType, false);
         curDiv = nullptr;
         continue;
@@ -4836,7 +4836,6 @@ HTMLEditRules::AlignBlockContents(nsIDOMNode* aNode,
   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();
 
@@ -4844,24 +4843,25 @@ HTMLEditRules::AlignBlockContents(nsIDOMNode* aNode,
   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;
       }
@@ -4869,28 +4869,29 @@ HTMLEditRules::AlignBlockContents(nsIDOMNode* aNode,
   } 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);
@@ -6480,10 +6481,14 @@ HTMLEditRules::SplitParagraph(nsIDOMNode *aPara,
   // split the paragraph
   NS_ENSURE_STATE(mHTMLEditor);
   NS_ENSURE_STATE(selNode->IsContent());
-  mHTMLEditor->SplitNodeDeep(*para, *selNode->AsContent(), *aOffset,
-                             HTMLEditor::EmptyContainers::yes,
-                             getter_AddRefs(leftPara),
-                             getter_AddRefs(rightPara));
+  int32_t offset =
+    mHTMLEditor->SplitNodeDeep(*para, *selNode->AsContent(), *aOffset,
+                               HTMLEditor::EmptyContainers::yes,
+                               getter_AddRefs(leftPara),
+                               getter_AddRefs(rightPara));
+  if (NS_WARN_IF(offset == -1)) {
+    return NS_ERROR_FAILURE;
+  }
   // get rid of the break, if it is visible (otherwise it may be needed to prevent an empty p)
   NS_ENSURE_STATE(mHTMLEditor);
   if (mHTMLEditor->IsVisBreak(aBRNode)) {
@@ -6493,9 +6498,9 @@ HTMLEditRules::SplitParagraph(nsIDOMNode *aPara,
   }
 
   // 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
@@ -7125,9 +7130,9 @@ HTMLEditRules::CacheInlineStyles(nsIDOMNode* aNode)
                                               isSet, &outValue);
     } else {
       NS_ENSURE_STATE(mHTMLEditor);
-      mHTMLEditor->mCSSEditUtils->IsCSSEquivalentToHTMLInlineStyleSet(aNode,
-        mCachedStyles[j].tag, &(mCachedStyles[j].attr), isSet, outValue,
-        CSSEditUtils::eComputed);
+      isSet = mHTMLEditor->mCSSEditUtils->IsCSSEquivalentToHTMLInlineStyleSet(
+                aNode, mCachedStyles[j].tag, &(mCachedStyles[j].attr), outValue,
+                CSSEditUtils::eComputed);
     }
     if (isSet) {
       mCachedStyles[j].mPresent = true;
@@ -8356,18 +8361,18 @@ HTMLEditRules::RemoveAlignment(nsIDOMNode* aNode,
       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;
@@ -8487,21 +8492,17 @@ HTMLEditRules::AlignBlock(Element& aElement,
   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);
     }
   }
diff --git a/editor/libeditor/HTMLEditor.cpp b/editor/libeditor/HTMLEditor.cpp
index 532da7a15..0a2ec023a 100644
--- a/editor/libeditor/HTMLEditor.cpp
+++ b/editor/libeditor/HTMLEditor.cpp
@@ -2584,7 +2584,7 @@ HTMLEditor::CreateElementWithDefaults(const nsAString& aTagName)
 
   // 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;
   }
@@ -2616,8 +2616,7 @@ HTMLEditor::CreateElementWithDefaults(const nsAString& aTagName)
   } 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
@@ -4443,87 +4442,83 @@ HTMLEditor::IsEmptyNodeImpl(nsINode* aNode,
 // add to aElement the CSS inline styles corresponding to the HTML attribute
 // aAttribute with its value aValue
 nsresult
-HTMLEditor::SetAttributeOrEquivalent(nsIDOMElement* aElement,
-                                     const nsAString& aAttribute,
+HTMLEditor::SetAttributeOrEquivalent(Element* aElement,
+                                     nsIAtom* aAttribute,
                                      const nsAString& aValue,
                                      bool aSuppressTransaction)
 {
+  MOZ_ASSERT(aElement);
+  MOZ_ASSERT(aAttribute);
+
   nsAutoScriptBlocker scriptBlocker;
 
-  if (IsCSSEnabled() && mCSSEditUtils) {
-    int32_t count;
-    nsresult rv =
-      mCSSEditUtils->SetCSSEquivalentToHTMLStyle(aElement, nullptr,
-                                                 &aAttribute, &aValue,
-                                                 &count,
-                                                 aSuppressTransaction);
-    NS_ENSURE_SUCCESS(rv, rv);
-    if (count) {
-      // we found an equivalence ; let's remove the HTML attribute itself if it is set
-      nsAutoString existingValue;
-      bool wasSet = false;
-      rv = GetAttributeValue(aElement, aAttribute, existingValue, &wasSet);
-      NS_ENSURE_SUCCESS(rv, rv);
-      if (!wasSet) {
-        return NS_OK;
-      }
-      return aSuppressTransaction ? aElement->RemoveAttribute(aAttribute) :
-                                    RemoveAttribute(aElement, aAttribute);
+  if (!IsCSSEnabled() || !mCSSEditUtils) {
+    // we are not in an HTML+CSS editor; let's set the attribute the HTML way
+    return aSuppressTransaction ?
+             aElement->SetAttr(kNameSpaceID_None, aAttribute, aValue, true) :
+             SetAttribute(aElement, aAttribute, aValue);
+  }
+
+  int32_t count =
+    mCSSEditUtils->SetCSSEquivalentToHTMLStyle(aElement, nullptr,
+                                               aAttribute, &aValue,
+                                               aSuppressTransaction);
+  if (count) {
+    // we found an equivalence ; let's remove the HTML attribute itself if it
+    // is set
+    nsAutoString existingValue;
+    if (!aElement->GetAttr(kNameSpaceID_None, aAttribute, existingValue)) {
+      return NS_OK;
     }
 
-    // count is an integer that represents the number of CSS declarations applied to the
-    // element. If it is zero, we found no equivalence in this implementation for the
-    // attribute
-    if (aAttribute.EqualsLiteral("style")) {
-      // if it is the style attribute, just add the new value to the existing style
-      // attribute's value
-      nsAutoString existingValue;
-      bool wasSet = false;
-      nsresult rv = GetAttributeValue(aElement, NS_LITERAL_STRING("style"),
-                                      existingValue, &wasSet);
-      NS_ENSURE_SUCCESS(rv, rv);
-      existingValue.Append(' ');
-      existingValue.Append(aValue);
-      return aSuppressTransaction ?
-        aElement->SetAttribute(aAttribute, existingValue) :
-        SetAttribute(aElement, aAttribute, existingValue);
-    }
+    return aSuppressTransaction ?
+             aElement->UnsetAttr(kNameSpaceID_None, aAttribute, true) :
+             RemoveAttribute(aElement, aAttribute);
+  }
 
-    // we have no CSS equivalence for this attribute and it is not the style
-    // attribute; let's set it the good'n'old HTML way
-    return aSuppressTransaction ? aElement->SetAttribute(aAttribute, aValue) :
-                                  SetAttribute(aElement, aAttribute, aValue);
+  // count is an integer that represents the number of CSS declarations applied
+  // to the element. If it is zero, we found no equivalence in this
+  // implementation for the attribute
+  if (aAttribute == nsGkAtoms::style) {
+    // if it is the style attribute, just add the new value to the existing
+    // style attribute's value
+    nsAutoString existingValue;
+    aElement->GetAttr(kNameSpaceID_None, nsGkAtoms::style, existingValue);
+    existingValue.Append(' ');
+    existingValue.Append(aValue);
+    return aSuppressTransaction ?
+       aElement->SetAttr(kNameSpaceID_None, aAttribute, existingValue, true) :
+      SetAttribute(aElement, aAttribute, existingValue);
   }
 
-  // we are not in an HTML+CSS editor; let's set the attribute the HTML way
-  return aSuppressTransaction ? aElement->SetAttribute(aAttribute, aValue) :
-                                SetAttribute(aElement, aAttribute, aValue);
+  // we have no CSS equivalence for this attribute and it is not the style
+  // attribute; let's set it the good'n'old HTML way
+  return aSuppressTransaction ?
+           aElement->SetAttr(kNameSpaceID_None, aAttribute, aValue, true) :
+           SetAttribute(aElement, aAttribute, aValue);
 }
 
 nsresult
-HTMLEditor::RemoveAttributeOrEquivalent(nsIDOMElement* aElement,
-                                        const nsAString& aAttribute,
+HTMLEditor::RemoveAttributeOrEquivalent(Element* aElement,
+                                        nsIAtom* aAttribute,
                                         bool aSuppressTransaction)
 {
-  nsCOMPtr<dom::Element> element = do_QueryInterface(aElement);
-  NS_ENSURE_TRUE(element, NS_OK);
-
-  nsCOMPtr<nsIAtom> attribute = NS_Atomize(aAttribute);
-  MOZ_ASSERT(attribute);
+  MOZ_ASSERT(aElement);
+  MOZ_ASSERT(aAttribute);
 
   if (IsCSSEnabled() && mCSSEditUtils) {
     nsresult rv =
       mCSSEditUtils->RemoveCSSEquivalentToHTMLStyle(
-        element, nullptr, &aAttribute, nullptr, aSuppressTransaction);
+        aElement, nullptr, aAttribute, nullptr, aSuppressTransaction);
     NS_ENSURE_SUCCESS(rv, rv);
   }
 
-  if (!element->HasAttr(kNameSpaceID_None, attribute)) {
+  if (!aElement->HasAttr(kNameSpaceID_None, aAttribute)) {
     return NS_OK;
   }
 
   return aSuppressTransaction ?
-    element->UnsetAttr(kNameSpaceID_None, attribute, /* aNotify = */ true) :
+    aElement->UnsetAttr(kNameSpaceID_None, aAttribute, /* aNotify = */ true) :
     RemoveAttribute(aElement, aAttribute);
 }
 
@@ -4576,7 +4571,6 @@ HTMLEditor::SetCSSBackgroundColor(const nsAString& aColor)
   NS_ENSURE_SUCCESS(rv, rv);
   if (!cancel && !handled) {
     // Loop through the ranges in the selection
-    NS_NAMED_LITERAL_STRING(bgcolor, "bgcolor");
     for (uint32_t i = 0; i < selection->RangeCount(); i++) {
       RefPtr<nsRange> range = selection->GetRangeAt(i);
       NS_ENSURE_TRUE(range, NS_ERROR_FAILURE);
@@ -4595,13 +4589,15 @@ HTMLEditor::SetCSSBackgroundColor(const nsAString& aColor)
         if (blockParent && cachedBlockParent != blockParent) {
           cachedBlockParent = blockParent;
           mCSSEditUtils->SetCSSEquivalentToHTMLStyle(blockParent, nullptr,
-                                                     &bgcolor, &aColor, false);
+                                                     nsGkAtoms::bgcolor,
+                                                     &aColor, false);
         }
       } else if (startNode == endNode &&
                  startNode->IsHTMLElement(nsGkAtoms::body) && isCollapsed) {
         // No block in the document, let's apply the background to the body
         mCSSEditUtils->SetCSSEquivalentToHTMLStyle(startNode->AsElement(),
-                                                   nullptr, &bgcolor, &aColor,
+                                                   nullptr, nsGkAtoms::bgcolor,
+                                                   &aColor,
                                                    false);
       } else if (startNode == endNode && (endOffset - startOffset == 1 ||
                                           (!startOffset && !endOffset))) {
@@ -4612,7 +4608,8 @@ HTMLEditor::SetCSSBackgroundColor(const nsAString& aColor)
         if (blockParent && cachedBlockParent != blockParent) {
           cachedBlockParent = blockParent;
           mCSSEditUtils->SetCSSEquivalentToHTMLStyle(blockParent, nullptr,
-                                                     &bgcolor, &aColor, false);
+                                                     nsGkAtoms::bgcolor,
+                                                     &aColor, false);
         }
       } else {
         // Not the easy case.  Range not contained in single text node.  There
@@ -4655,7 +4652,8 @@ HTMLEditor::SetCSSBackgroundColor(const nsAString& aColor)
           if (blockParent && cachedBlockParent != blockParent) {
             cachedBlockParent = blockParent;
             mCSSEditUtils->SetCSSEquivalentToHTMLStyle(blockParent, nullptr,
-                                                       &bgcolor, &aColor,
+                                                       nsGkAtoms::bgcolor,
+                                                       &aColor,
                                                        false);
           }
         }
@@ -4666,7 +4664,8 @@ HTMLEditor::SetCSSBackgroundColor(const nsAString& aColor)
           if (blockParent && cachedBlockParent != blockParent) {
             cachedBlockParent = blockParent;
             mCSSEditUtils->SetCSSEquivalentToHTMLStyle(blockParent, nullptr,
-                                                       &bgcolor, &aColor,
+                                                       nsGkAtoms::bgcolor,
+                                                       &aColor,
                                                        false);
           }
         }
@@ -4680,7 +4679,8 @@ HTMLEditor::SetCSSBackgroundColor(const nsAString& aColor)
           if (blockParent && cachedBlockParent != blockParent) {
             cachedBlockParent = blockParent;
             mCSSEditUtils->SetCSSEquivalentToHTMLStyle(blockParent, nullptr,
-                                                       &bgcolor, &aColor,
+                                                       nsGkAtoms::bgcolor,
+                                                       &aColor,
                                                        false);
           }
         }
diff --git a/editor/libeditor/HTMLEditor.h b/editor/libeditor/HTMLEditor.h
index dfcdd8d6b..090e3f56c 100644
--- a/editor/libeditor/HTMLEditor.h
+++ b/editor/libeditor/HTMLEditor.h
@@ -118,6 +118,16 @@ public:
   virtual already_AddRefed<nsIContent> GetInputEventTargetContent() override;
   virtual bool IsEditable(nsINode* aNode) override;
   using EditorBase::IsEditable;
+  virtual nsresult RemoveAttributeOrEquivalent(
+                     Element* aElement,
+                     nsIAtom* aAttribute,
+                     bool aSuppressTransaction) override;
+  virtual nsresult SetAttributeOrEquivalent(Element* aElement,
+                                            nsIAtom* aAttribute,
+                                            const nsAString& aValue,
+                                            bool aSuppressTransaction) override;
+  using EditorBase::RemoveAttributeOrEquivalent;
+  using EditorBase::SetAttributeOrEquivalent;
 
   // nsStubMutationObserver overrides
   NS_DECL_NSIMUTATIONOBSERVER_CONTENTAPPENDED
@@ -329,14 +339,6 @@ public:
    */
   virtual nsresult SelectEntireDocument(Selection* aSelection) override;
 
-  NS_IMETHOD SetAttributeOrEquivalent(nsIDOMElement* aElement,
-                                      const nsAString& aAttribute,
-                                      const nsAString& aValue,
-                                      bool aSuppressTransaction) override;
-  NS_IMETHOD RemoveAttributeOrEquivalent(nsIDOMElement* aElement,
-                                         const nsAString& aAttribute,
-                                         bool aSuppressTransaction) override;
-
   /**
    * Join together any adjacent editable text nodes in the range.
    */
diff --git a/editor/libeditor/HTMLEditorObjectResizer.cpp b/editor/libeditor/HTMLEditorObjectResizer.cpp
index 111a3f975..8ed5b6e4d 100644
--- a/editor/libeditor/HTMLEditorObjectResizer.cpp
+++ b/editor/libeditor/HTMLEditorObjectResizer.cpp
@@ -926,35 +926,30 @@ HTMLEditor::SetFinalSize(int32_t aX,
   // 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 {
@@ -964,30 +959,30 @@ HTMLEditor::SetFinalSize(int32_t aX,
     // 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());
     }
   }
diff --git a/editor/libeditor/HTMLStyleEditor.cpp b/editor/libeditor/HTMLStyleEditor.cpp
index c81ca1c53..1a10dc830 100644
--- a/editor/libeditor/HTMLStyleEditor.cpp
+++ b/editor/libeditor/HTMLStyleEditor.cpp
@@ -429,7 +429,7 @@ HTMLEditor::SetInlinePropertyOnNodeImpl(nsIContent& aNode,
                  mCSSEditUtils->IsCSSEditableProperty(&aNode, &aProperty,
                                                       aAttribute)) ||
                 // bgcolor is always done using CSS
-                aAttribute->EqualsLiteral("bgcolor");
+                attrAtom == nsGkAtoms::bgcolor;
 
   if (useCSS) {
     nsCOMPtr<dom::Element> tmp;
@@ -444,12 +444,9 @@ HTMLEditor::SetInlinePropertyOnNodeImpl(nsIContent& aNode,
     }
 
     // Add the CSS styles corresponding to the HTML style request
-    int32_t count;
-    nsresult rv =
-      mCSSEditUtils->SetCSSEquivalentToHTMLStyle(tmp->AsDOMNode(),
-                                                 &aProperty, aAttribute,
-                                                 &aValue, &count, false);
-    NS_ENSURE_SUCCESS(rv, rv);
+    mCSSEditUtils->SetCSSEquivalentToHTMLStyle(tmp,
+                                               &aProperty, attrAtom,
+                                               &aValue, false);
     return NS_OK;
   }
 
@@ -574,8 +571,9 @@ HTMLEditor::SplitStyleAbovePoint(nsCOMPtr<nsINode>* aNode,
       // in this implementation for the node; let's check if it carries those
       // CSS styles
       nsAutoString firstValue;
-      mCSSEditUtils->IsCSSEquivalentToHTMLInlineStyleSet(GetAsDOMNode(node),
-        aProperty, aAttribute, isSet, firstValue, CSSEditUtils::eSpecified);
+      isSet = mCSSEditUtils->IsCSSEquivalentToHTMLInlineStyleSet(
+                node, aProperty, aAttribute, firstValue,
+                CSSEditUtils::eSpecified);
     }
     if (// node is the correct inline prop
         (aProperty && node->IsHTMLElement(aProperty)) ||
@@ -744,8 +742,6 @@ HTMLEditor::RemoveStyleInside(nsIContent& 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);
@@ -754,14 +750,14 @@ HTMLEditor::RemoveStyleInside(nsIContent& aNode,
         // 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);
@@ -794,15 +790,17 @@ HTMLEditor::RemoveStyleInside(nsIContent& aNode,
     // the HTML style defined by aProperty/aAttribute has a CSS equivalence in
     // this implementation for the node aNode; let's check if it carries those
     // css styles
+    nsCOMPtr<nsIAtom> attribute =
+      aAttribute ? NS_Atomize(*aAttribute) : nullptr;
     nsAutoString propertyValue;
     bool isSet = mCSSEditUtils->IsCSSEquivalentToHTMLInlineStyleSet(&aNode,
-      aProperty, aAttribute, propertyValue, CSSEditUtils::eSpecified);
+      aProperty, attribute, propertyValue, CSSEditUtils::eSpecified);
     if (isSet && aNode.IsElement()) {
       // yes, tmp has the corresponding css declarations in its style attribute
       // let's remove them
       mCSSEditUtils->RemoveCSSEquivalentToHTMLStyle(aNode.AsElement(),
                                                     aProperty,
-                                                    aAttribute,
+                                                    attribute,
                                                     &propertyValue,
                                                     false);
       // remove the node if it is a span or font, if its style attribute is
diff --git a/editor/libeditor/TextEditRules.cpp b/editor/libeditor/TextEditRules.cpp
index 8f8f34e8b..d441b49eb 100644
--- a/editor/libeditor/TextEditRules.cpp
+++ b/editor/libeditor/TextEditRules.cpp
@@ -25,7 +25,6 @@
 #include "nsError.h"
 #include "nsGkAtoms.h"
 #include "nsIContent.h"
-#include "nsIDOMCharacterData.h"
 #include "nsIDOMDocument.h"
 #include "nsIDOMElement.h"
 #include "nsIDOMNode.h"
@@ -482,26 +481,24 @@ TextEditRules::CollapseSelectionToTrailingBRIfNeeded(Selection* aSelection)
   return NS_OK;
 }
 
-static inline already_AddRefed<nsIDOMNode>
-GetTextNode(Selection* selection,
-            EditorBase* editor)
+static inline already_AddRefed<nsINode>
+GetTextNode(Selection* selection)
 {
   int32_t selOffset;
-  nsCOMPtr<nsIDOMNode> selNode;
+  nsCOMPtr<nsINode> selNode;
   nsresult rv =
-    editor->GetStartNodeAndOffset(selection,
-                                  getter_AddRefs(selNode), &selOffset);
+    EditorBase::GetStartNodeAndOffset(selection,
+                                      getter_AddRefs(selNode), &selOffset);
   NS_ENSURE_SUCCESS(rv, nullptr);
-  if (!editor->IsTextNode(selNode)) {
-    // Get an nsINode from the nsIDOMNode
-    nsCOMPtr<nsINode> node = do_QueryInterface(selNode);
-    // if node is null, return it to indicate there's no text
-    NS_ENSURE_TRUE(node, nullptr);
+  if (!EditorBase::IsTextNode(selNode)) {
     // This should be the root node, walk the tree looking for text nodes
     RefPtr<NodeIterator> iter =
-      new NodeIterator(node, nsIDOMNodeFilter::SHOW_TEXT, NodeFilterHolder());
-    while (!editor->IsTextNode(selNode)) {
-      if (NS_FAILED(iter->NextNode(getter_AddRefs(selNode))) || !selNode) {
+      new NodeIterator(selNode, nsIDOMNodeFilter::SHOW_TEXT,
+                       NodeFilterHolder());
+    while (!EditorBase::IsTextNode(selNode)) {
+      IgnoredErrorResult rv;
+      selNode = iter->NextNode(rv);
+      if (!selNode) {
         return nullptr;
       }
     }
@@ -1385,13 +1382,10 @@ TextEditRules::HideLastPWInput()
   nsContentUtils::GetSelectionInTextControl(selection, mTextEditor->GetRoot(),
                                             start, end);
 
-  nsCOMPtr<nsIDOMNode> selNode = GetTextNode(selection, mTextEditor);
+  nsCOMPtr<nsINode> selNode = GetTextNode(selection);
   NS_ENSURE_TRUE(selNode, NS_OK);
 
-  nsCOMPtr<nsIDOMCharacterData> nodeAsText(do_QueryInterface(selNode));
-  NS_ENSURE_TRUE(nodeAsText, NS_OK);
-
-  nodeAsText->ReplaceData(mLastStart, mLastLength, hiddenText);
+  selNode->GetAsText()->ReplaceData(mLastStart, mLastLength, hiddenText);
   selection->Collapse(selNode, start);
   if (start != end) {
     selection->Extend(selNode, end);
@@ -1431,9 +1425,9 @@ TextEditRules::CreateMozBR(nsIDOMNode* inParent,
   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);
   }
diff --git a/editor/libeditor/TextEditor.cpp b/editor/libeditor/TextEditor.cpp
index 1e855d769..d7284c4c2 100644
--- a/editor/libeditor/TextEditor.cpp
+++ b/editor/libeditor/TextEditor.cpp
@@ -310,9 +310,9 @@ TextEditor::UpdateMetaCharset(nsIDOMDocument* aDocument,
     }
 
     // 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));
@@ -1621,8 +1621,8 @@ TextEditor::GetDOMEventTarget()
 
 
 nsresult
-TextEditor::SetAttributeOrEquivalent(nsIDOMElement* aElement,
-                                     const nsAString& aAttribute,
+TextEditor::SetAttributeOrEquivalent(Element* aElement,
+                                     nsIAtom* aAttribute,
                                      const nsAString& aValue,
                                      bool aSuppressTransaction)
 {
@@ -1630,8 +1630,8 @@ TextEditor::SetAttributeOrEquivalent(nsIDOMElement* aElement,
 }
 
 nsresult
-TextEditor::RemoveAttributeOrEquivalent(nsIDOMElement* aElement,
-                                        const nsAString& aAttribute,
+TextEditor::RemoveAttributeOrEquivalent(Element* aElement,
+                                        nsIAtom* aAttribute,
                                         bool aSuppressTransaction)
 {
   return EditorBase::RemoveAttribute(aElement, aAttribute);
diff --git a/editor/libeditor/TextEditor.h b/editor/libeditor/TextEditor.h
index 31c551f85..7bb594931 100644
--- a/editor/libeditor/TextEditor.h
+++ b/editor/libeditor/TextEditor.h
@@ -63,14 +63,17 @@ public:
   // nsIEditorMailSupport overrides
   NS_DECL_NSIEDITORMAILSUPPORT
 
-  // Overrides of EditorBase interface methods
-  NS_IMETHOD SetAttributeOrEquivalent(nsIDOMElement* aElement,
-                                      const nsAString& aAttribute,
-                                      const nsAString& aValue,
-                                      bool aSuppressTransaction) override;
-  NS_IMETHOD RemoveAttributeOrEquivalent(nsIDOMElement* aElement,
-                                         const nsAString& aAttribute,
-                                         bool aSuppressTransaction) override;
+  // Overrides of EditorBase
+  virtual nsresult RemoveAttributeOrEquivalent(
+                     Element* aElement,
+                     nsIAtom* aAttribute,
+                     bool aSuppressTransaction) override;
+  virtual nsresult SetAttributeOrEquivalent(Element* aElement,
+                                            nsIAtom* aAttribute,
+                                            const nsAString& aValue,
+                                            bool aSuppressTransaction) override;
+  using EditorBase::RemoveAttributeOrEquivalent;
+  using EditorBase::SetAttributeOrEquivalent;
 
   NS_IMETHOD Init(nsIDOMDocument* aDoc, nsIContent* aRoot,
                   nsISelectionController* aSelCon, uint32_t aFlags,