diff --git a/dom/base/nsContentListDeclarations.h b/dom/base/nsContentListDeclarations.h
index db3a09036bb1..a5e0e3691bd4 100644
--- a/dom/base/nsContentListDeclarations.h
+++ b/dom/base/nsContentListDeclarations.h
@@ -18,6 +18,12 @@ class nsINode;
 class nsString;
 class nsAString;
 
+namespace mozilla {
+namespace dom {
+class Element;
+} // namespace dom
+} // namespace mozilla
+
 // Magic namespace id that means "match all namespaces".  This is
 // negative so it won't collide with actual namespace constants.
 #define kNameSpaceID_Wildcard INT32_MIN
@@ -26,7 +32,7 @@ class nsAString;
 // arbitrary matching algorithm.  aContent is the content that may
 // match the list, while aNamespaceID, aAtom, and aData are whatever
 // was passed to the list's constructor.
-typedef bool (*nsContentListMatchFunc)(nsIContent* aContent,
+typedef bool (*nsContentListMatchFunc)(mozilla::dom::Element* aElement,
                                        int32_t aNamespaceID,
                                        nsIAtom* aAtom,
                                        void* aData);
diff --git a/dom/base/nsContentUtils.cpp b/dom/base/nsContentUtils.cpp
index 50533e37cdf2..4547244d72aa 100644
--- a/dom/base/nsContentUtils.cpp
+++ b/dom/base/nsContentUtils.cpp
@@ -6349,11 +6349,11 @@ struct ClassMatchingInfo {
 
 // static
 bool
-nsContentUtils::MatchClassNames(nsIContent* aContent, int32_t aNamespaceID,
+nsContentUtils::MatchClassNames(Element* aElement, int32_t aNamespaceID,
                                 nsIAtom* aAtom, void* aData)
 {
   // We can't match if there are no class names
-  const nsAttrValue* classAttr = aContent->GetClasses();
+  const nsAttrValue* classAttr = aElement->GetClasses();
   if (!classAttr) {
     return false;
   }
diff --git a/dom/base/nsContentUtils.h b/dom/base/nsContentUtils.h
index 87f32aac367e..bc7b6cebd5c3 100644
--- a/dom/base/nsContentUtils.h
+++ b/dom/base/nsContentUtils.h
@@ -2827,7 +2827,8 @@ private:
 
   static void DropFragmentParsers();
 
-  static bool MatchClassNames(nsIContent* aContent, int32_t aNamespaceID,
+  static bool MatchClassNames(mozilla::dom::Element* aElement,
+                              int32_t aNamespaceID,
                               nsIAtom* aAtom, void* aData);
   static void DestroyClassNameArray(void* aData);
   static void* AllocClassMatchingInfo(nsINode* aRootNode,
diff --git a/dom/html/HTMLAllCollection.cpp b/dom/html/HTMLAllCollection.cpp
index afa160e0ced1..6305cce31c8e 100644
--- a/dom/html/HTMLAllCollection.cpp
+++ b/dom/html/HTMLAllCollection.cpp
@@ -8,6 +8,7 @@
 
 #include "mozilla/dom/HTMLAllCollectionBinding.h"
 #include "mozilla/dom/Nullable.h"
+#include "mozilla/dom/Element.h"
 #include "nsHTMLDocument.h"
 
 namespace mozilla {
@@ -86,14 +87,14 @@ IsAllNamedElement(nsIContent* aContent)
 }
 
 static bool
-DocAllResultMatch(nsIContent* aContent, int32_t aNamespaceID, nsIAtom* aAtom,
+DocAllResultMatch(Element* aElement, int32_t aNamespaceID, nsIAtom* aAtom,
                   void* aData)
 {
-  if (aContent->GetID() == aAtom) {
+  if (aElement->GetID() == aAtom) {
     return true;
   }
 
-  nsGenericHTMLElement* elm = nsGenericHTMLElement::FromContent(aContent);
+  nsGenericHTMLElement* elm = nsGenericHTMLElement::FromContent(aElement);
   if (!elm) {
     return false;
   }
diff --git a/dom/html/HTMLDataListElement.cpp b/dom/html/HTMLDataListElement.cpp
index d9ad4da0913e..5aa772645d84 100644
--- a/dom/html/HTMLDataListElement.cpp
+++ b/dom/html/HTMLDataListElement.cpp
@@ -35,11 +35,11 @@ NS_INTERFACE_MAP_END_INHERITING(nsGenericHTMLElement)
 NS_IMPL_ELEMENT_CLONE(HTMLDataListElement)
 
 bool
-HTMLDataListElement::MatchOptions(nsIContent* aContent, int32_t aNamespaceID,
+HTMLDataListElement::MatchOptions(Element* aElement, int32_t aNamespaceID,
                                   nsIAtom* aAtom, void* aData)
 {
-  return aContent->NodeInfo()->Equals(nsGkAtoms::option, kNameSpaceID_XHTML) &&
-         !aContent->HasAttr(kNameSpaceID_None, nsGkAtoms::disabled);
+  return aElement->NodeInfo()->Equals(nsGkAtoms::option, kNameSpaceID_XHTML) &&
+         !aElement->HasAttr(kNameSpaceID_None, nsGkAtoms::disabled);
 }
 
 } // namespace dom
diff --git a/dom/html/HTMLDataListElement.h b/dom/html/HTMLDataListElement.h
index e0aff818be82..ba2a2e0b41cd 100644
--- a/dom/html/HTMLDataListElement.h
+++ b/dom/html/HTMLDataListElement.h
@@ -37,8 +37,8 @@ public:
   virtual nsresult Clone(mozilla::dom::NodeInfo *aNodeInfo, nsINode **aResult) const override;
 
   // This function is used to generate the nsContentList (option elements).
-  static bool MatchOptions(nsIContent* aContent, int32_t aNamespaceID,
-                             nsIAtom* aAtom, void* aData);
+  static bool MatchOptions(Element* aElement, int32_t aNamespaceID,
+                           nsIAtom* aAtom, void* aData);
 
   NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(HTMLDataListElement,
                                            nsGenericHTMLElement)
diff --git a/dom/html/HTMLFieldSetElement.cpp b/dom/html/HTMLFieldSetElement.cpp
index db55425e748b..c008b9b6d65b 100644
--- a/dom/html/HTMLFieldSetElement.cpp
+++ b/dom/html/HTMLFieldSetElement.cpp
@@ -120,10 +120,10 @@ HTMLFieldSetElement::GetType(nsAString& aType)
 
 /* static */
 bool
-HTMLFieldSetElement::MatchListedElements(nsIContent* aContent, int32_t aNamespaceID,
+HTMLFieldSetElement::MatchListedElements(Element* aElement, int32_t aNamespaceID,
                                          nsIAtom* aAtom, void* aData)
 {
-  nsCOMPtr<nsIFormControl> formControl = do_QueryInterface(aContent);
+  nsCOMPtr<nsIFormControl> formControl = do_QueryInterface(aElement);
   return formControl;
 }
 
diff --git a/dom/html/HTMLFieldSetElement.h b/dom/html/HTMLFieldSetElement.h
index 3341ba365554..1e9f0214f56c 100644
--- a/dom/html/HTMLFieldSetElement.h
+++ b/dom/html/HTMLFieldSetElement.h
@@ -125,8 +125,8 @@ private:
   void NotifyElementsForFirstLegendChange(bool aNotify);
 
   // This function is used to generate the nsContentList (listed form elements).
-  static bool MatchListedElements(nsIContent* aContent, int32_t aNamespaceID,
-                                    nsIAtom* aAtom, void* aData);
+  static bool MatchListedElements(Element* aElement, int32_t aNamespaceID,
+                                  nsIAtom* aAtom, void* aData);
 
   // listed form controls elements.
   RefPtr<nsContentList> mElements;
diff --git a/dom/html/HTMLSelectElement.cpp b/dom/html/HTMLSelectElement.cpp
index 5ac3692ffbf1..0f4dbaa87733 100644
--- a/dom/html/HTMLSelectElement.cpp
+++ b/dom/html/HTMLSelectElement.cpp
@@ -748,12 +748,12 @@ HTMLSelectElement::SetLength(uint32_t aLength, ErrorResult& aRv)
 
 /* static */
 bool
-HTMLSelectElement::MatchSelectedOptions(nsIContent* aContent,
+HTMLSelectElement::MatchSelectedOptions(Element* aElement,
                                         int32_t /* unused */,
                                         nsIAtom* /* unused */,
                                         void* /* unused*/)
 {
-  HTMLOptionElement* option = HTMLOptionElement::FromContent(aContent);
+  HTMLOptionElement* option = HTMLOptionElement::FromContent(aElement);
   return option && option->Selected();
 }
 
diff --git a/dom/html/HTMLSelectElement.h b/dom/html/HTMLSelectElement.h
index 9f8bdf5f4854..e3ed588538f4 100644
--- a/dom/html/HTMLSelectElement.h
+++ b/dom/html/HTMLSelectElement.h
@@ -252,7 +252,7 @@ public:
     mOptions->IndexedSetter(aIndex, aOption, aRv);
   }
 
-  static bool MatchSelectedOptions(nsIContent* aContent, int32_t, nsIAtom*,
+  static bool MatchSelectedOptions(Element* aElement, int32_t, nsIAtom*,
                                    void*);
 
   nsIHTMLCollection* SelectedOptions();
diff --git a/dom/html/HTMLTableRowElement.cpp b/dom/html/HTMLTableRowElement.cpp
index bb8aca3f4bce..86edeebb0e43 100644
--- a/dom/html/HTMLTableRowElement.cpp
+++ b/dom/html/HTMLTableRowElement.cpp
@@ -120,10 +120,10 @@ HTMLTableRowElement::SectionRowIndex() const
 }
 
 static bool
-IsCell(nsIContent *aContent, int32_t aNamespaceID,
+IsCell(Element *aElement, int32_t aNamespaceID,
        nsIAtom* aAtom, void *aData)
 {
-  return aContent->IsAnyOfHTMLElements(nsGkAtoms::td, nsGkAtoms::th);
+  return aElement->IsAnyOfHTMLElements(nsGkAtoms::td, nsGkAtoms::th);
 }
 
 nsIHTMLCollection*
diff --git a/dom/html/nsHTMLDocument.cpp b/dom/html/nsHTMLDocument.cpp
index 1c441fef194b..5ad22c4f399b 100644
--- a/dom/html/nsHTMLDocument.cpp
+++ b/dom/html/nsHTMLDocument.cpp
@@ -1105,31 +1105,31 @@ nsHTMLDocument::Applets()
 }
 
 bool
-nsHTMLDocument::MatchLinks(nsIContent *aContent, int32_t aNamespaceID,
+nsHTMLDocument::MatchLinks(Element* aElement, int32_t aNamespaceID,
                            nsIAtom* aAtom, void* aData)
 {
-  nsIDocument* doc = aContent->GetUncomposedDoc();
+  nsIDocument* doc = aElement->GetUncomposedDoc();
 
   if (doc) {
-    NS_ASSERTION(aContent->IsInUncomposedDoc(),
+    NS_ASSERTION(aElement->IsInUncomposedDoc(),
                  "This method should never be called on content nodes that "
                  "are not in a document!");
 #ifdef DEBUG
     {
       nsCOMPtr<nsIHTMLDocument> htmldoc =
-        do_QueryInterface(aContent->GetUncomposedDoc());
+        do_QueryInterface(aElement->GetUncomposedDoc());
       NS_ASSERTION(htmldoc,
                    "Huh, how did this happen? This should only be used with "
                    "HTML documents!");
     }
 #endif
 
-    mozilla::dom::NodeInfo *ni = aContent->NodeInfo();
+    mozilla::dom::NodeInfo *ni = aElement->NodeInfo();
 
     nsIAtom *localName = ni->NameAtom();
     if (ni->NamespaceID() == kNameSpaceID_XHTML &&
         (localName == nsGkAtoms::a || localName == nsGkAtoms::area)) {
-      return aContent->HasAttr(kNameSpaceID_None, nsGkAtoms::href);
+      return aElement->HasAttr(kNameSpaceID_None, nsGkAtoms::href);
     }
   }
 
@@ -1153,24 +1153,24 @@ nsHTMLDocument::Links()
 }
 
 bool
-nsHTMLDocument::MatchAnchors(nsIContent *aContent, int32_t aNamespaceID,
+nsHTMLDocument::MatchAnchors(Element* aElement, int32_t aNamespaceID,
                              nsIAtom* aAtom, void* aData)
 {
-  NS_ASSERTION(aContent->IsInUncomposedDoc(),
+  NS_ASSERTION(aElement->IsInUncomposedDoc(),
                "This method should never be called on content nodes that "
                "are not in a document!");
 #ifdef DEBUG
   {
     nsCOMPtr<nsIHTMLDocument> htmldoc =
-      do_QueryInterface(aContent->GetUncomposedDoc());
+      do_QueryInterface(aElement->GetUncomposedDoc());
     NS_ASSERTION(htmldoc,
                  "Huh, how did this happen? This should only be used with "
                  "HTML documents!");
   }
 #endif
 
-  if (aContent->NodeInfo()->Equals(nsGkAtoms::a, kNameSpaceID_XHTML)) {
-    return aContent->HasAttr(kNameSpaceID_None, nsGkAtoms::name);
+  if (aElement->IsHTMLElement(nsGkAtoms::a)) {
+    return aElement->HasAttr(kNameSpaceID_None, nsGkAtoms::name);
   }
 
   return false;
@@ -1947,14 +1947,14 @@ nsHTMLDocument::Writeln(JSContext* cx, const Sequence<nsString>& aText,
 }
 
 bool
-nsHTMLDocument::MatchNameAttribute(nsIContent* aContent, int32_t aNamespaceID,
+nsHTMLDocument::MatchNameAttribute(Element* aElement, int32_t aNamespaceID,
                                    nsIAtom* aAtom, void* aData)
 {
-  NS_PRECONDITION(aContent, "Must have content node to work with!");
+  NS_PRECONDITION(aElement, "Must have element to work with!");
   nsString* elementName = static_cast<nsString*>(aData);
   return
-    aContent->GetNameSpaceID() == kNameSpaceID_XHTML &&
-    aContent->AttrValueIs(kNameSpaceID_None, nsGkAtoms::name,
+    aElement->GetNameSpaceID() == kNameSpaceID_XHTML &&
+    aElement->AttrValueIs(kNameSpaceID_None, nsGkAtoms::name,
                           *elementName, eCaseMatters);
 }
 
@@ -2274,10 +2274,10 @@ nsHTMLDocument::GetForms()
   return mForms;
 }
 
-static bool MatchFormControls(nsIContent* aContent, int32_t aNamespaceID,
-                                nsIAtom* aAtom, void* aData)
+static bool MatchFormControls(Element* aElement, int32_t aNamespaceID,
+                              nsIAtom* aAtom, void* aData)
 {
-  return aContent->IsNodeOfType(nsIContent::eHTML_FORM_CONTROL);
+  return aElement->IsNodeOfType(nsIContent::eHTML_FORM_CONTROL);
 }
 
 nsContentList*
diff --git a/dom/html/nsHTMLDocument.h b/dom/html/nsHTMLDocument.h
index a55a64b41ddb..18d8a6ac4c0c 100644
--- a/dom/html/nsHTMLDocument.h
+++ b/dom/html/nsHTMLDocument.h
@@ -260,12 +260,13 @@ protected:
 
   nsIContent *MatchId(nsIContent *aContent, const nsAString& aId);
 
-  static bool MatchLinks(nsIContent *aContent, int32_t aNamespaceID,
+  static bool MatchLinks(mozilla::dom::Element* aElement, int32_t aNamespaceID,
+                         nsIAtom* aAtom, void* aData);
+  static bool MatchAnchors(mozilla::dom::Element* aElement, int32_t aNamespaceID,
                            nsIAtom* aAtom, void* aData);
-  static bool MatchAnchors(nsIContent *aContent, int32_t aNamespaceID,
-                             nsIAtom* aAtom, void* aData);
-  static bool MatchNameAttribute(nsIContent* aContent, int32_t aNamespaceID,
-                                   nsIAtom* aAtom, void* aData);
+  static bool MatchNameAttribute(mozilla::dom::Element* aElement,
+                                 int32_t aNamespaceID,
+                                 nsIAtom* aAtom, void* aData);
   static void* UseExistingNameString(nsINode* aRootNode, const nsString* aName);
 
   static void DocumentWriteTerminationFunc(nsISupports *aRef);
diff --git a/dom/xul/XULDocument.cpp b/dom/xul/XULDocument.cpp
index a3b99685a794..79adebd0da48 100644
--- a/dom/xul/XULDocument.cpp
+++ b/dom/xul/XULDocument.cpp
@@ -1932,26 +1932,26 @@ XULDocument::StartLayout(void)
 
 /* static */
 bool
-XULDocument::MatchAttribute(nsIContent* aContent,
+XULDocument::MatchAttribute(Element* aElement,
                             int32_t aNamespaceID,
                             nsIAtom* aAttrName,
                             void* aData)
 {
-    NS_PRECONDITION(aContent, "Must have content node to work with!");
+    NS_PRECONDITION(aElement, "Must have content node to work with!");
     nsString* attrValue = static_cast<nsString*>(aData);
     if (aNamespaceID != kNameSpaceID_Unknown &&
         aNamespaceID != kNameSpaceID_Wildcard) {
         return attrValue->EqualsLiteral("*") ?
-            aContent->HasAttr(aNamespaceID, aAttrName) :
-            aContent->AttrValueIs(aNamespaceID, aAttrName, *attrValue,
+            aElement->HasAttr(aNamespaceID, aAttrName) :
+            aElement->AttrValueIs(aNamespaceID, aAttrName, *attrValue,
                                   eCaseMatters);
     }
 
     // Qualified name match. This takes more work.
 
-    uint32_t count = aContent->GetAttrCount();
+    uint32_t count = aElement->GetAttrCount();
     for (uint32_t i = 0; i < count; ++i) {
-        const nsAttrName* name = aContent->GetAttrNameAt(i);
+        const nsAttrName* name = aElement->GetAttrNameAt(i);
         bool nameMatch;
         if (name->IsAtom()) {
             nameMatch = name->Atom() == aAttrName;
@@ -1963,7 +1963,7 @@ XULDocument::MatchAttribute(nsIContent* aContent,
 
         if (nameMatch) {
             return attrValue->EqualsLiteral("*") ||
-                aContent->AttrValueIs(name->NamespaceID(), name->LocalName(),
+                aElement->AttrValueIs(name->NamespaceID(), name->LocalName(),
                                       *attrValue, eCaseMatters);
         }
     }
diff --git a/dom/xul/XULDocument.h b/dom/xul/XULDocument.h
index 7325d8dc1137..16eafb792d09 100644
--- a/dom/xul/XULDocument.h
+++ b/dom/xul/XULDocument.h
@@ -179,7 +179,7 @@ public:
     NS_IMETHOD OnScriptCompileComplete(JSScript* aScript, nsresult aStatus) override;
 
     static bool
-    MatchAttribute(nsIContent* aContent,
+    MatchAttribute(Element* aContent,
                    int32_t aNameSpaceID,
                    nsIAtom* aAttrName,
                    void* aData);