diff --git a/accessible/base/AccIterator.cpp b/accessible/base/AccIterator.cpp
index d1e7b4e1ff8..80412cda99e 100644
--- a/accessible/base/AccIterator.cpp
+++ b/accessible/base/AccIterator.cpp
@@ -141,7 +141,7 @@ HTMLLabelIterator::Next()
   // element, or <label> ancestor which implicitly point to it.
   Accessible* label = nullptr;
   while ((label = mRelIter.Next())) {
-    if (label->GetContent()->Tag() == nsGkAtoms::label)
+    if (label->GetContent()->IsHTMLElement(nsGkAtoms::label))
       return label;
   }
 
@@ -155,17 +155,15 @@ HTMLLabelIterator::Next()
   Accessible* walkUp = mAcc->Parent();
   while (walkUp && !walkUp->IsDoc()) {
     nsIContent* walkUpElm = walkUp->GetContent();
-    if (walkUpElm->IsHTMLElement()) {
-      if (walkUpElm->Tag() == nsGkAtoms::label &&
-          !walkUpElm->HasAttr(kNameSpaceID_None, nsGkAtoms::_for)) {
-        mLabelFilter = eSkipAncestorLabel; // prevent infinite loop
-        return walkUp;
-      }
-
-      if (walkUpElm->Tag() == nsGkAtoms::form)
-        break;
+    if (walkUpElm->IsHTMLElement(nsGkAtoms::label) &&
+        !walkUpElm->HasAttr(kNameSpaceID_None, nsGkAtoms::_for)) {
+      mLabelFilter = eSkipAncestorLabel; // prevent infinite loop
+      return walkUp;
     }
 
+    if (walkUpElm->IsHTMLElement(nsGkAtoms::form))
+      break;
+
     walkUp = walkUp->Parent();
   }
 
@@ -188,7 +186,7 @@ HTMLOutputIterator::Next()
 {
   Accessible* output = nullptr;
   while ((output = mRelIter.Next())) {
-    if (output->GetContent()->Tag() == nsGkAtoms::output)
+    if (output->GetContent()->IsHTMLElement(nsGkAtoms::output))
       return output;
   }
 
@@ -211,7 +209,7 @@ XULLabelIterator::Next()
 {
   Accessible* label = nullptr;
   while ((label = mRelIter.Next())) {
-    if (label->GetContent()->Tag() == nsGkAtoms::label)
+    if (label->GetContent()->IsXULElement(nsGkAtoms::label))
       return label;
   }
 
@@ -234,7 +232,7 @@ XULDescriptionIterator::Next()
 {
   Accessible* descr = nullptr;
   while ((descr = mRelIter.Next())) {
-    if (descr->GetContent()->Tag() == nsGkAtoms::description)
+    if (descr->GetContent()->IsXULElement(nsGkAtoms::description))
       return descr;
   }
 
diff --git a/accessible/base/Logging.cpp b/accessible/base/Logging.cpp
index 0975307f9b2..a080c35e57a 100644
--- a/accessible/base/Logging.cpp
+++ b/accessible/base/Logging.cpp
@@ -713,7 +713,7 @@ logging::Node(const char* aDescr, nsINode* aNode)
   dom::Element* elm = aNode->AsElement();
 
   nsAutoCString tag;
-  elm->Tag()->ToUTF8String(tag);
+  elm->NodeInfo()->NameAtom()->ToUTF8String(tag);
 
   nsIAtom* idAtom = elm->GetID();
   nsAutoCString id;
diff --git a/accessible/base/TextAttrs.cpp b/accessible/base/TextAttrs.cpp
index 62b02a30088..cf19f2054c4 100644
--- a/accessible/base/TextAttrs.cpp
+++ b/accessible/base/TextAttrs.cpp
@@ -872,11 +872,10 @@ TextAttrsMgr::TextPosTextAttr::
   }
 
   const nsIContent* content = aFrame->GetContent();
-  if (content && content->IsHTMLElement()) {
-    const nsIAtom* tagName = content->Tag();
-    if (tagName == nsGkAtoms::sup)
+  if (content) {
+    if (content->IsHTMLElement(nsGkAtoms::sup))
       return eTextPosSuper;
-    if (tagName == nsGkAtoms::sub)
+    if (content->IsHTMLElement(nsGkAtoms::sub))
       return eTextPosSub;
   }
 
diff --git a/accessible/base/nsAccessibilityService.cpp b/accessible/base/nsAccessibilityService.cpp
index 68dc6c358c4..f98aa29894d 100644
--- a/accessible/base/nsAccessibilityService.cpp
+++ b/accessible/base/nsAccessibilityService.cpp
@@ -893,8 +893,7 @@ nsAccessibilityService::GetOrCreateAccessible(nsINode* aNode,
 
 #ifdef DEBUG
   nsImageFrame* imageFrame = do_QueryFrame(frame);
-  NS_ASSERTION(imageFrame && content->IsHTMLElement() &&
-               content->Tag() == nsGkAtoms::area,
+  NS_ASSERTION(imageFrame && content->IsHTMLElement(nsGkAtoms::area),
                "Unknown case of not main content for the frame!");
 #endif
     return nullptr;
@@ -902,8 +901,7 @@ nsAccessibilityService::GetOrCreateAccessible(nsINode* aNode,
 
 #ifdef DEBUG
   nsImageFrame* imageFrame = do_QueryFrame(frame);
-  NS_ASSERTION(!imageFrame || !content->IsHTMLElement() ||
-               content->Tag() != nsGkAtoms::area,
+  NS_ASSERTION(!imageFrame || !content->IsHTMLElement(nsGkAtoms::area),
                "Image map manages the area accessible creation!");
 #endif
 
@@ -933,8 +931,7 @@ nsAccessibilityService::GetOrCreateAccessible(nsINode* aNode,
     return newAcc;
   }
 
-  bool isHTML = content->IsHTMLElement();
-  if (isHTML && content->Tag() == nsGkAtoms::map) {
+  if (content->IsHTMLElement(nsGkAtoms::map)) {
     // Create hyper text accessible for HTML map if it is used to group links
     // (see http://www.w3.org/TR/WCAG10-HTML-TECHS/#group-bypass). If the HTML
     // map rect is empty then it is used for links grouping. Otherwise it should
@@ -973,7 +970,7 @@ nsAccessibilityService::GetOrCreateAccessible(nsINode* aNode,
     roleMapEntry = nullptr;
   }
 
-  if (!newAcc && isHTML) {  // HTML accessibles
+  if (!newAcc && content->IsHTMLElement()) {  // HTML accessibles
     bool isARIATableOrCell = roleMapEntry &&
       (roleMapEntry->accTypes & (eTableCell | eTable));
 
@@ -1011,9 +1008,9 @@ nsAccessibilityService::GetOrCreateAccessible(nsINode* aNode,
                  aContext->ARIARoleMap() == &aria::gEmptyRoleMap) {
         roleMapEntry = &aria::gEmptyRoleMap;
 
-      } else if (content->Tag() == nsGkAtoms::dt ||
-                 content->Tag() == nsGkAtoms::li ||
-                 content->Tag() == nsGkAtoms::dd ||
+      } else if (content->IsAnyOfHTMLElements(nsGkAtoms::dt,
+                                              nsGkAtoms::li,
+                                              nsGkAtoms::dd) ||
                  frame->AccessibleType() == eHTMLLiType) {
         nsRoleMapEntry* contextRoleMap = aContext->ARIARoleMap();
         if (!contextRoleMap->IsOfType(eList))
@@ -1059,11 +1056,11 @@ nsAccessibilityService::GetOrCreateAccessible(nsINode* aNode,
         // polyline and image. A 'use' and 'text' graphic elements require
         // special support.
         newAcc = new EnumRoleAccessible(content, document, roles::GRAPHIC);
-      } else if (content->Tag() == nsGkAtoms::svg) {
+      } else if (content->IsSVGElement(nsGkAtoms::svg)) {
         newAcc = new EnumRoleAccessible(content, document, roles::DIAGRAM);
       }
     } else if (content->IsMathMLElement()) {
-      if (content->Tag() == nsGkAtoms::math)
+      if (content->IsMathMLElement(nsGkAtoms::math))
         newAcc = new EnumRoleAccessible(content, document, roles::EQUATION);
       else
         newAcc = new HyperTextAccessible(content, document);
@@ -1074,13 +1071,15 @@ nsAccessibilityService::GetOrCreateAccessible(nsINode* aNode,
   // of some property that makes this object interesting
   // We don't do this for <body>, <html>, <window>, <dialog> etc. which
   // correspond to the doc accessible and will be created in any case
-  if (!newAcc && content->Tag() != nsGkAtoms::body && content->GetParent() &&
+  if (!newAcc && !content->IsHTMLElement(nsGkAtoms::body) &&
+      content->GetParent() &&
       (roleMapEntry || MustBeAccessible(content, document) ||
-       (isHTML && nsCoreUtils::HasClickListener(content)))) {
+       (content->IsHTMLElement() &&
+        nsCoreUtils::HasClickListener(content)))) {
     // This content is focusable or has an interesting dynamic content accessibility property.
     // If it's interesting we need it in the accessibility hierarchy so that events or
     // other accessibles can point to it, or so that it can hold a state, etc.
-    if (isHTML) {
+    if (content->IsHTMLElement()) {
       // Interesting HTML container which may have selectable text and/or embedded objects
       newAcc = new HyperTextAccessibleWrap(content, document);
     } else {  // XUL, SVG, MathML etc.
@@ -1298,7 +1297,7 @@ nsAccessibilityService::CreateAccessibleByType(nsIContent* aContent,
     // implementations on each platform for a consistent scripting environment, but
     // then strip out redundant accessibles in the AccessibleWrap class for each platform.
     nsIContent *parent = aContent->GetParent();
-    if (parent && parent->IsXULElement() && parent->Tag() == nsGkAtoms::menu)
+    if (parent && parent->IsXULElement(nsGkAtoms::menu))
       return nullptr;
 #endif
 
@@ -1392,45 +1391,45 @@ nsAccessibilityService::CreateHTMLAccessibleByMarkup(nsIFrame* aFrame,
   }
 
   // This method assumes we're in an HTML namespace.
-  nsIAtom* tag = aContent->Tag();
-  if (tag == nsGkAtoms::figcaption) {
+  if (aContent->IsHTMLElement(nsGkAtoms::figcaption)) {
     nsRefPtr<Accessible> accessible =
       new HTMLFigcaptionAccessible(aContent, document);
     return accessible.forget();
   }
 
-  if (tag == nsGkAtoms::figure) {
+  if (aContent->IsHTMLElement(nsGkAtoms::figure)) {
     nsRefPtr<Accessible> accessible =
       new HTMLFigureAccessible(aContent, document);
     return accessible.forget();
   }
 
-  if (tag == nsGkAtoms::legend) {
+  if (aContent->IsHTMLElement(nsGkAtoms::legend)) {
     nsRefPtr<Accessible> accessible =
       new HTMLLegendAccessible(aContent, document);
     return accessible.forget();
   }
 
-  if (tag == nsGkAtoms::option) {
+  if (aContent->IsHTMLElement(nsGkAtoms::option)) {
     nsRefPtr<Accessible> accessible =
       new HTMLSelectOptionAccessible(aContent, document);
     return accessible.forget();
   }
 
-  if (tag == nsGkAtoms::optgroup) {
+  if (aContent->IsHTMLElement(nsGkAtoms::optgroup)) {
     nsRefPtr<Accessible> accessible =
       new HTMLSelectOptGroupAccessible(aContent, document);
     return accessible.forget();
   }
 
-  if (tag == nsGkAtoms::ul || tag == nsGkAtoms::ol ||
-      tag == nsGkAtoms::dl) {
+  if (aContent->IsAnyOfHTMLElements(nsGkAtoms::ul,
+                                    nsGkAtoms::ol,
+                                    nsGkAtoms::dl)) {
     nsRefPtr<Accessible> accessible =
       new HTMLListAccessible(aContent, document);
     return accessible.forget();
   }
 
-  if (tag == nsGkAtoms::a) {
+  if (aContent->IsHTMLElement(nsGkAtoms::a)) {
     // Only some roles truly enjoy life as HTMLLinkAccessibles, for details
     // see closed bug 494807.
     nsRoleMapEntry* roleMapEntry = aria::GetRoleMap(aContent);
@@ -1451,13 +1450,13 @@ nsAccessibilityService::CreateHTMLAccessibleByMarkup(nsIFrame* aFrame,
     // it unconditionally by tag name. nsBlockFrame creates the list item
     // accessible for other elements styled as list items.
     if (aContext->GetContent() == aContent->GetParent()) {
-      if (tag == nsGkAtoms::dt || tag == nsGkAtoms::li) {
+      if (aContent->IsAnyOfHTMLElements(nsGkAtoms::dt, nsGkAtoms::li)) {
         nsRefPtr<Accessible> accessible =
           new HTMLLIAccessible(aContent, document);
         return accessible.forget();
       }
 
-      if (tag == nsGkAtoms::dd) {
+      if (aContent->IsHTMLElement(nsGkAtoms::dd)) {
         nsRefPtr<Accessible> accessible =
           new HyperTextAccessibleWrap(aContent, document);
         return accessible.forget();
@@ -1467,42 +1466,42 @@ nsAccessibilityService::CreateHTMLAccessibleByMarkup(nsIFrame* aFrame,
     return nullptr;
   }
 
-  if (tag == nsGkAtoms::abbr ||
-      tag == nsGkAtoms::acronym ||
-      tag == nsGkAtoms::article ||
-      tag == nsGkAtoms::aside ||
-      tag == nsGkAtoms::blockquote ||
-      tag == nsGkAtoms::form ||
-      tag == nsGkAtoms::footer ||
-      tag == nsGkAtoms::header ||
-      tag == nsGkAtoms::h1 ||
-      tag == nsGkAtoms::h2 ||
-      tag == nsGkAtoms::h3 ||
-      tag == nsGkAtoms::h4 ||
-      tag == nsGkAtoms::h5 ||
-      tag == nsGkAtoms::h6 ||
-      tag == nsGkAtoms::nav ||
-      tag == nsGkAtoms::q ||
-      tag == nsGkAtoms::section ||
-      tag == nsGkAtoms::time) {
+  if (aContent->IsAnyOfHTMLElements(nsGkAtoms::abbr,
+                                    nsGkAtoms::acronym,
+                                    nsGkAtoms::article,
+                                    nsGkAtoms::aside,
+                                    nsGkAtoms::blockquote,
+                                    nsGkAtoms::form,
+                                    nsGkAtoms::footer,
+                                    nsGkAtoms::header,
+                                    nsGkAtoms::h1,
+                                    nsGkAtoms::h2,
+                                    nsGkAtoms::h3,
+                                    nsGkAtoms::h4,
+                                    nsGkAtoms::h5,
+                                    nsGkAtoms::h6,
+                                    nsGkAtoms::nav,
+                                    nsGkAtoms::q,
+                                    nsGkAtoms::section,
+                                    nsGkAtoms::time)) {
     nsRefPtr<Accessible> accessible =
       new HyperTextAccessibleWrap(aContent, document);
     return accessible.forget();
   }
 
-  if (tag == nsGkAtoms::label) {
+  if (aContent->IsHTMLElement(nsGkAtoms::label)) {
     nsRefPtr<Accessible> accessible =
       new HTMLLabelAccessible(aContent, document);
     return accessible.forget();
   }
 
-  if (tag == nsGkAtoms::output) {
+  if (aContent->IsHTMLElement(nsGkAtoms::output)) {
     nsRefPtr<Accessible> accessible =
       new HTMLOutputAccessible(aContent, document);
     return accessible.forget();
   }
 
-  if (tag == nsGkAtoms::progress) {
+  if (aContent->IsHTMLElement(nsGkAtoms::progress)) {
     nsRefPtr<Accessible> accessible =
       new HTMLProgressMeterAccessible(aContent, document);
     return accessible.forget();
@@ -1620,7 +1619,7 @@ nsAccessibilityService::CreateAccessibleByFrameType(nsIFrame* aFrame,
       newAcc = new HTMLTextFieldAccessible(aContent, document);
       break;
     case eHyperTextType:
-      if (aContent->Tag() != nsGkAtoms::dt && aContent->Tag() != nsGkAtoms::dd)
+      if (!aContent->IsAnyOfHTMLElements(nsGkAtoms::dt, nsGkAtoms::dd))
         newAcc = new HyperTextAccessibleWrap(aContent, document);
       break;
 
diff --git a/accessible/generic/Accessible.cpp b/accessible/generic/Accessible.cpp
index f924b2065c6..bcb8967f87f 100644
--- a/accessible/generic/Accessible.cpp
+++ b/accessible/generic/Accessible.cpp
@@ -354,8 +354,7 @@ Accessible::VisibilityState()
     nsIFrame* parentFrame = curFrame->GetParent();
     nsDeckFrame* deckFrame = do_QueryFrame(parentFrame);
     if (deckFrame && deckFrame->GetSelectedBox() != curFrame) {
-      if (deckFrame->GetContent()->IsXULElement() &&
-          deckFrame->GetContent()->Tag() == nsGkAtoms::tabpanels)
+      if (deckFrame->GetContent()->IsXULElement(nsGkAtoms::tabpanels))
         return states::OFFSCREEN;
 
       NS_NOTREACHED("Children of not selected deck panel are not accessible.");
@@ -820,7 +819,7 @@ Accessible::XULElmName(DocAccessible* aDocument,
   nsIContent* parent =
     bindingParent? bindingParent->GetParent() : aElm->GetParent();
   while (parent) {
-    if (parent->Tag() == nsGkAtoms::toolbaritem &&
+    if (parent->IsXULElement(nsGkAtoms::toolbaritem) &&
         parent->GetAttr(kNameSpaceID_None, nsGkAtoms::title, aName)) {
       aName.CompressWhitespace();
       return;
@@ -1531,7 +1530,7 @@ Accessible::RelationByType(RelationType aType)
     case RelationType::LABEL_FOR: {
       Relation rel(new RelatedAccIterator(Document(), mContent,
                                           nsGkAtoms::aria_labelledby));
-      if (mContent->Tag() == nsGkAtoms::label && mContent->IsXULElement())
+      if (mContent->IsXULElement(nsGkAtoms::label))
         rel.AppendIter(new IDRefsIterator(mDoc, mContent, nsGkAtoms::control));
 
       return rel;
@@ -1553,8 +1552,7 @@ Accessible::RelationByType(RelationType aType)
       // This affectively adds an optional control attribute to xul:description,
       // which only affects accessibility, by allowing the description to be
       // tied to a control.
-      if (mContent->Tag() == nsGkAtoms::description &&
-          mContent->IsXULElement())
+      if (mContent->IsXULElement(nsGkAtoms::description))
         rel.AppendIter(new IDRefsIterator(mDoc, mContent,
                                           nsGkAtoms::control));
 
diff --git a/accessible/generic/Accessible.h b/accessible/generic/Accessible.h
index d61fb72bf9d..d613d3f76ec 100644
--- a/accessible/generic/Accessible.h
+++ b/accessible/generic/Accessible.h
@@ -565,8 +565,7 @@ public:
 
   inline bool IsAbbreviation() const
   {
-    return mContent->IsHTMLElement() &&
-      (mContent->Tag() == nsGkAtoms::abbr || mContent->Tag() == nsGkAtoms::acronym);
+    return mContent->IsAnyOfHTMLElements(nsGkAtoms::abbr, nsGkAtoms::acronym);
   }
 
   bool IsApplication() const { return mType == eApplicationType; }
diff --git a/accessible/generic/DocAccessible.cpp b/accessible/generic/DocAccessible.cpp
index a404ed1036d..86ef9e5e51e 100644
--- a/accessible/generic/DocAccessible.cpp
+++ b/accessible/generic/DocAccessible.cpp
@@ -1500,15 +1500,13 @@ DocAccessible::AddDependentIDsFor(dom::Element* aRelProviderElm,
       continue;
 
     if (relAttr == nsGkAtoms::_for) {
-      if (!aRelProviderElm->IsHTMLElement() ||
-          (aRelProviderElm->Tag() != nsGkAtoms::label &&
-           aRelProviderElm->Tag() != nsGkAtoms::output))
+      if (!aRelProviderElm->IsAnyOfHTMLElements(nsGkAtoms::label,
+                                                nsGkAtoms::output))
         continue;
 
     } else if (relAttr == nsGkAtoms::control) {
-      if (!aRelProviderElm->IsXULElement() ||
-          (aRelProviderElm->Tag() != nsGkAtoms::label &&
-           aRelProviderElm->Tag() != nsGkAtoms::description))
+      if (!aRelProviderElm->IsAnyOfXULElements(nsGkAtoms::label,
+                                               nsGkAtoms::description))
         continue;
     }
 
diff --git a/accessible/generic/HyperTextAccessible.cpp b/accessible/generic/HyperTextAccessible.cpp
index bd1180ba3ab..9d5a9356ddd 100644
--- a/accessible/generic/HyperTextAccessible.cpp
+++ b/accessible/generic/HyperTextAccessible.cpp
@@ -59,34 +59,34 @@ NS_IMPL_ISUPPORTS_INHERITED0(HyperTextAccessible, Accessible)
 role
 HyperTextAccessible::NativeRole()
 {
-  nsIAtom *tag = mContent->Tag();
-
-  if (tag == nsGkAtoms::dd)
+  if (mContent->IsHTMLElement(nsGkAtoms::dd))
     return roles::DEFINITION;
 
-  if (tag == nsGkAtoms::form)
+  if (mContent->IsHTMLElement(nsGkAtoms::form))
     return roles::FORM;
 
-  if (tag == nsGkAtoms::blockquote || tag == nsGkAtoms::div ||
-      tag == nsGkAtoms::section || tag == nsGkAtoms::nav)
+  if (mContent->IsAnyOfHTMLElements(nsGkAtoms::blockquote,
+                                    nsGkAtoms::div,
+                                    nsGkAtoms::section,
+                                    nsGkAtoms::nav))
     return roles::SECTION;
 
-  if (tag == nsGkAtoms::h1 || tag == nsGkAtoms::h2 ||
-      tag == nsGkAtoms::h3 || tag == nsGkAtoms::h4 ||
-      tag == nsGkAtoms::h5 || tag == nsGkAtoms::h6)
+  if (mContent->IsAnyOfHTMLElements(nsGkAtoms::h1, nsGkAtoms::h2,
+                                    nsGkAtoms::h3, nsGkAtoms::h4,
+                                    nsGkAtoms::h5, nsGkAtoms::h6))
     return roles::HEADING;
 
-  if (tag == nsGkAtoms::article)
+  if (mContent->IsHTMLElement(nsGkAtoms::article))
     return roles::DOCUMENT;
 
   // Deal with html landmark elements
-  if (tag == nsGkAtoms::header)
+  if (mContent->IsHTMLElement(nsGkAtoms::header))
     return roles::HEADER;
 
-  if (tag == nsGkAtoms::footer)
+  if (mContent->IsHTMLElement(nsGkAtoms::footer))
     return roles::FOOTER;
 
-  if (tag == nsGkAtoms::aside)
+  if (mContent->IsHTMLElement(nsGkAtoms::aside))
     return roles::NOTE;
 
   // Treat block frames as paragraphs
@@ -105,7 +105,7 @@ HyperTextAccessible::NativeState()
   if (mContent->AsElement()->State().HasState(NS_EVENT_STATE_MOZ_READWRITE)) {
     states |= states::EDITABLE;
 
-  } else if (mContent->Tag() == nsGkAtoms::article) {
+  } else if (mContent->IsHTMLElement(nsGkAtoms::article)) {
     // We want <article> to behave like a document in terms of readonly state.
     states |= states::READONLY;
   }
@@ -900,18 +900,17 @@ HyperTextAccessible::DefaultTextAttributes()
 int32_t
 HyperTextAccessible::GetLevelInternal()
 {
-  nsIAtom *tag = mContent->Tag();
-  if (tag == nsGkAtoms::h1)
+  if (mContent->IsHTMLElement(nsGkAtoms::h1))
     return 1;
-  if (tag == nsGkAtoms::h2)
+  if (mContent->IsHTMLElement(nsGkAtoms::h2))
     return 2;
-  if (tag == nsGkAtoms::h3)
+  if (mContent->IsHTMLElement(nsGkAtoms::h3))
     return 3;
-  if (tag == nsGkAtoms::h4)
+  if (mContent->IsHTMLElement(nsGkAtoms::h4))
     return 4;
-  if (tag == nsGkAtoms::h5)
+  if (mContent->IsHTMLElement(nsGkAtoms::h5))
     return 5;
-  if (tag == nsGkAtoms::h6)
+  if (mContent->IsHTMLElement(nsGkAtoms::h6))
     return 6;
 
   return AccessibleWrap::GetLevelInternal();
@@ -944,14 +943,13 @@ HyperTextAccessible::NativeAttributes()
   if (!HasOwnContent())
     return attributes.forget();
 
-  nsIAtom* tag = mContent->Tag();
-  if (tag == nsGkAtoms::section)  {
+  if (mContent->IsHTMLElement(nsGkAtoms::section)) {
     nsAccUtils::SetAccAttr(attributes, nsGkAtoms::xmlroles,
                            NS_LITERAL_STRING("region"));
-  } else if (tag == nsGkAtoms::article) {
+  } else if (mContent->IsHTMLElement(nsGkAtoms::article)) {
     nsAccUtils::SetAccAttr(attributes, nsGkAtoms::xmlroles,
                            NS_LITERAL_STRING("article"));
-  } else if (tag == nsGkAtoms::time) {
+  } else if (mContent->IsHTMLElement(nsGkAtoms::time)) {
     nsAccUtils::SetAccAttr(attributes, nsGkAtoms::xmlroles,
                            NS_LITERAL_STRING("time"));
 
@@ -970,38 +968,42 @@ HyperTextAccessible::LandmarkRole() const
 {
   // For the html landmark elements we expose them like we do ARIA landmarks to
   // make AT navigation schemes "just work".
-  nsIAtom* tag = mContent->Tag();
-  if (tag == nsGkAtoms::nav)
+  if (mContent->IsHTMLElement(nsGkAtoms::nav)) {
     return nsGkAtoms::navigation;
+  }
 
-  if (tag == nsGkAtoms::header || tag == nsGkAtoms::footer) {
+  if (mContent->IsAnyOfHTMLElements(nsGkAtoms::header,
+                                    nsGkAtoms::footer)) {
     // Only map header and footer if they are not descendants of an article
     // or section tag.
     nsIContent* parent = mContent->GetParent();
     while (parent) {
-      if (parent->Tag() == nsGkAtoms::article ||
-          parent->Tag() == nsGkAtoms::section)
+      if (parent->IsAnyOfHTMLElements(nsGkAtoms::article, nsGkAtoms::section)) {
         break;
+      }
       parent = parent->GetParent();
     }
 
     // No article or section elements found.
     if (!parent) {
-      if (tag == nsGkAtoms::header)
+      if (mContent->IsHTMLElement(nsGkAtoms::header)) {
         return nsGkAtoms::banner;
+      }
 
-      if (tag == nsGkAtoms::footer) {
+      if (mContent->IsHTMLElement(nsGkAtoms::footer)) {
         return nsGkAtoms::contentinfo;
       }
     }
     return nullptr;
   }
 
-  if (tag == nsGkAtoms::aside)
+  if (mContent->IsHTMLElement(nsGkAtoms::aside)) {
     return nsGkAtoms::complementary;
+  }
 
-  if (tag == nsGkAtoms::main)
+  if (mContent->IsHTMLElement(nsGkAtoms::main)) {
     return nsGkAtoms::main;
+  }
 
   return nullptr;
 }
diff --git a/accessible/generic/RootAccessible.cpp b/accessible/generic/RootAccessible.cpp
index e98e7636f2b..801e473ce5c 100644
--- a/accessible/generic/RootAccessible.cpp
+++ b/accessible/generic/RootAccessible.cpp
@@ -92,8 +92,8 @@ RootAccessible::NativeRole()
 {
   // If it's a <dialog> or <wizard>, use roles::DIALOG instead
   dom::Element* rootElm = mDocumentNode->GetRootElement();
-  if (rootElm && (rootElm->Tag() == nsGkAtoms::dialog ||
-                  rootElm->Tag() == nsGkAtoms::wizard))
+  if (rootElm && rootElm->IsAnyOfXULElements(nsGkAtoms::dialog,
+                                             nsGkAtoms::wizard))
     return roles::DIALOG;
 
   return DocAccessibleWrap::NativeRole();
diff --git a/accessible/html/HTMLFormControlAccessible.cpp b/accessible/html/HTMLFormControlAccessible.cpp
index 8846eed7815..9d655bbee6e 100644
--- a/accessible/html/HTMLFormControlAccessible.cpp
+++ b/accessible/html/HTMLFormControlAccessible.cpp
@@ -250,7 +250,7 @@ HTMLButtonAccessible::NativeName(nsString& aName)
   // type="submit"/"reset"/"image" elements.
 
   ENameValueFlag nameFlag = Accessible::NativeName(aName);
-  if (!aName.IsEmpty() || mContent->Tag() != nsGkAtoms::input ||
+  if (!aName.IsEmpty() || !mContent->IsHTMLElement(nsGkAtoms::input) ||
       !mContent->AttrValueIs(kNameSpaceID_None, nsGkAtoms::type,
                              nsGkAtoms::image, eCaseMatters))
     return nameFlag;
diff --git a/accessible/html/HTMLListAccessible.cpp b/accessible/html/HTMLListAccessible.cpp
index 182fc13c4df..533a38ea804 100644
--- a/accessible/html/HTMLListAccessible.cpp
+++ b/accessible/html/HTMLListAccessible.cpp
@@ -26,7 +26,7 @@ NS_IMPL_ISUPPORTS_INHERITED0(HTMLListAccessible, HyperTextAccessible)
 role
 HTMLListAccessible::NativeRole()
 {
-  if (mContent->Tag() == nsGkAtoms::dl)
+  if (mContent->IsHTMLElement(nsGkAtoms::dl))
     return roles::DEFINITION_LIST;
 
   return roles::LIST;
@@ -69,7 +69,7 @@ HTMLLIAccessible::Shutdown()
 role
 HTMLLIAccessible::NativeRole()
 {
-  if (mContent->Tag() == nsGkAtoms::dt)
+  if (mContent->IsHTMLElement(nsGkAtoms::dt))
     return roles::TERM;
 
   return roles::LISTITEM;
diff --git a/accessible/html/HTMLSelectAccessible.cpp b/accessible/html/HTMLSelectAccessible.cpp
index 5f9fb503893..5a905a373ce 100644
--- a/accessible/html/HTMLSelectAccessible.cpp
+++ b/accessible/html/HTMLSelectAccessible.cpp
@@ -130,9 +130,8 @@ HTMLSelectListAccessible::CacheChildren()
       continue;
     }
 
-    nsIAtom* tag = childContent->Tag();
-    if (tag == nsGkAtoms::option ||
-        tag == nsGkAtoms::optgroup) {
+    if (childContent->IsAnyOfHTMLElements(nsGkAtoms::option,
+                                          nsGkAtoms::optgroup)) {
 
       // Get an accessible for option or optgroup and cache it.
       nsRefPtr<Accessible> accessible =
diff --git a/accessible/html/HTMLTableAccessible.cpp b/accessible/html/HTMLTableAccessible.cpp
index 5aae851451d..e6ae5d43a26 100644
--- a/accessible/html/HTMLTableAccessible.cpp
+++ b/accessible/html/HTMLTableAccessible.cpp
@@ -929,7 +929,7 @@ HTMLTableAccessible::IsProbablyLayoutTable()
     RETURN_LAYOUT_ANSWER(false, "Has role attribute, weak role, and role is table");
   }
 
-  if (mContent->Tag() != nsGkAtoms::table)
+  if (!mContent->IsHTMLElement(nsGkAtoms::table))
     RETURN_LAYOUT_ANSWER(true, "table built by CSS display:table style");
 
   // Check if datatable attribute has "0" value.
@@ -954,18 +954,18 @@ HTMLTableAccessible::IsProbablyLayoutTable()
     if (!childElm->IsHTMLElement())
       continue;
 
-    if (childElm->Tag() == nsGkAtoms::col ||
-        childElm->Tag() == nsGkAtoms::colgroup ||
-        childElm->Tag() == nsGkAtoms::tfoot ||
-        childElm->Tag() == nsGkAtoms::thead) {
+    if (childElm->IsAnyOfHTMLElements(nsGkAtoms::col,
+                                      nsGkAtoms::colgroup,
+                                      nsGkAtoms::tfoot,
+                                      nsGkAtoms::thead)) {
       RETURN_LAYOUT_ANSWER(false,
                            "Has col, colgroup, tfoot or thead -- legitimate table structures");
     }
 
-    if (childElm->Tag() == nsGkAtoms::tbody) {
+    if (childElm->IsHTMLElement(nsGkAtoms::tbody)) {
       for (nsIContent* rowElm = childElm->GetFirstChild(); rowElm;
            rowElm = rowElm->GetNextSibling()) {
-        if (rowElm->IsHTMLElement() && rowElm->Tag() == nsGkAtoms::tr) {
+        if (rowElm->IsHTMLElement(nsGkAtoms::tr)) {
           for (nsIContent* cellElm = rowElm->GetFirstChild(); cellElm;
                cellElm = cellElm->GetNextSibling()) {
             if (cellElm->IsHTMLElement()) {
diff --git a/accessible/windows/msaa/AccessibleWrap.cpp b/accessible/windows/msaa/AccessibleWrap.cpp
index ae04aadb479..253441a6676 100644
--- a/accessible/windows/msaa/AccessibleWrap.cpp
+++ b/accessible/windows/msaa/AccessibleWrap.cpp
@@ -1221,7 +1221,7 @@ AccessibleWrap::HandleAccEvent(AccEvent* aEvent)
   nsAutoCString id;
   nsIContent* cnt = accessible->GetContent();
   if (cnt) {
-    cnt->Tag()->ToString(tag);
+    cnt->NodeInfo()->NameAtom()->ToString(tag);
     nsIAtom* aid = cnt->GetID();
     if (aid)
       aid->ToUTF8String(id);
diff --git a/accessible/xul/XULElementAccessibles.cpp b/accessible/xul/XULElementAccessibles.cpp
index 58843f7d7b2..629545628c0 100644
--- a/accessible/xul/XULElementAccessibles.cpp
+++ b/accessible/xul/XULElementAccessibles.cpp
@@ -92,7 +92,7 @@ XULLabelAccessible::RelationByType(RelationType aType)
   if (aType == RelationType::LABEL_FOR) {
     // Caption is the label for groupbox
     nsIContent* parent = mContent->GetFlattenedTreeParent();
-    if (parent && parent->Tag() == nsGkAtoms::caption) {
+    if (parent && parent->IsXULElement(nsGkAtoms::caption)) {
       Accessible* parent = Parent();
       if (parent && parent->Role() == roles::GROUPING)
         rel.AppendTarget(parent);
diff --git a/accessible/xul/XULFormControlAccessible.cpp b/accessible/xul/XULFormControlAccessible.cpp
index 98bda6ad46c..8eb104e2a1b 100644
--- a/accessible/xul/XULFormControlAccessible.cpp
+++ b/accessible/xul/XULFormControlAccessible.cpp
@@ -182,7 +182,7 @@ XULButtonAccessible::IsAcceptableChild(Accessible* aPossibleChild) const
   // Button type="menu-button" contains a real button. Get an accessible
   // for it. Ignore dropmarker button which is placed as a last child.
   if (role != roles::PUSHBUTTON ||
-      aPossibleChild->GetContent()->Tag() == nsGkAtoms::dropMarker)
+      aPossibleChild->GetContent()->IsXULElement(nsGkAtoms::dropMarker))
     return false;
 
   return mContent->AttrValueIs(kNameSpaceID_None, nsGkAtoms::type,
@@ -569,9 +569,10 @@ bool
 XULToolbarButtonAccessible::IsSeparator(Accessible* aAccessible)
 {
   nsIContent* content = aAccessible->GetContent();
-  return content && ((content->Tag() == nsGkAtoms::toolbarseparator) ||
-                     (content->Tag() == nsGkAtoms::toolbarspacer) ||
-                     (content->Tag() == nsGkAtoms::toolbarspring)); }
+  return content && content->IsAnyOfXULElements(nsGkAtoms::toolbarseparator,
+                                                nsGkAtoms::toolbarspacer,
+                                                nsGkAtoms::toolbarspring);
+}
 
 
 ////////////////////////////////////////////////////////////////////////////////