diff --git a/parser/html/nsHtml5TreeOperation.cpp b/parser/html/nsHtml5TreeOperation.cpp
index 732fde4a7fe1..62178bc1b238 100644
--- a/parser/html/nsHtml5TreeOperation.cpp
+++ b/parser/html/nsHtml5TreeOperation.cpp
@@ -42,7 +42,6 @@
 
 using namespace mozilla;
 using namespace mozilla::dom;
-using mozilla::dom::Document;
 
 /**
  * Helper class that opens a notification batch if the current doc
@@ -208,7 +207,7 @@ nsHtml5TreeOperation::~nsHtml5TreeOperation() {
 }
 
 nsresult nsHtml5TreeOperation::AppendTextToTextNode(
-    const char16_t* aBuffer, uint32_t aLength, dom::Text* aTextNode,
+    const char16_t* aBuffer, uint32_t aLength, Text* aTextNode,
     nsHtml5DocumentBuilder* aBuilder) {
   MOZ_ASSERT(aTextNode, "Got null text node.");
   MOZ_ASSERT(aBuilder);
@@ -259,12 +258,12 @@ nsresult nsHtml5TreeOperation::Append(nsIContent* aNode, nsIContent* aParent,
 }
 
 nsresult nsHtml5TreeOperation::Append(nsIContent* aNode, nsIContent* aParent,
-                                      mozilla::dom::FromParser aFromParser,
+                                      FromParser aFromParser,
                                       nsHtml5DocumentBuilder* aBuilder) {
   Maybe<nsHtml5AutoPauseUpdate> autoPause;
-  Maybe<dom::AutoCEReaction> autoCEReaction;
-  dom::DocGroup* docGroup = aParent->OwnerDoc()->GetDocGroup();
-  if (docGroup && aFromParser != mozilla::dom::FROM_PARSER_FRAGMENT) {
+  Maybe<AutoCEReaction> autoCEReaction;
+  DocGroup* docGroup = aParent->OwnerDoc()->GetDocGroup();
+  if (docGroup && aFromParser != FROM_PARSER_FRAGMENT) {
     autoCEReaction.emplace(docGroup->CustomElementReactionsStack(), nullptr);
   }
   nsresult rv = Append(aNode, aParent, aBuilder);
@@ -385,7 +384,7 @@ nsresult nsHtml5TreeOperation::FosterParent(nsIContent* aNode,
 nsresult nsHtml5TreeOperation::AddAttributes(nsIContent* aNode,
                                              nsHtml5HtmlAttributes* aAttributes,
                                              nsHtml5DocumentBuilder* aBuilder) {
-  dom::Element* node = aNode->AsElement();
+  Element* node = aNode->AsElement();
   nsHtml5OtherDocUpdate update(node->OwnerDoc(), aBuilder->GetDocument());
 
   int32_t len = aAttributes->getLength();
@@ -405,7 +404,7 @@ nsresult nsHtml5TreeOperation::AddAttributes(nsIContent* aNode,
 }
 
 void nsHtml5TreeOperation::SetHTMLElementAttributes(
-    dom::Element* aElement, nsAtom* aName, nsHtml5HtmlAttributes* aAttributes) {
+    Element* aElement, nsAtom* aName, nsHtml5HtmlAttributes* aAttributes) {
   int32_t len = aAttributes->getLength();
   for (int32_t i = 0; i < len; i++) {
     nsHtml5String val = aAttributes->getValueNoBoundsCheck(i);
@@ -504,38 +503,37 @@ nsIContent* nsHtml5TreeOperation::CreateHTMLElement(
 }
 
 nsIContent* nsHtml5TreeOperation::CreateSVGElement(
-    nsAtom* aName, nsHtml5HtmlAttributes* aAttributes,
-    mozilla::dom::FromParser aFromParser, nsNodeInfoManager* aNodeInfoManager,
-    nsHtml5DocumentBuilder* aBuilder,
-    mozilla::dom::SVGContentCreatorFunction aCreator) {
+    nsAtom* aName, nsHtml5HtmlAttributes* aAttributes, FromParser aFromParser,
+    nsNodeInfoManager* aNodeInfoManager, nsHtml5DocumentBuilder* aBuilder,
+    SVGContentCreatorFunction aCreator) {
   nsCOMPtr<nsIContent> newElement;
   if (MOZ_LIKELY(aNodeInfoManager->SVGEnabled())) {
-    RefPtr<dom::NodeInfo> nodeInfo = aNodeInfoManager->GetNodeInfo(
+    RefPtr<NodeInfo> nodeInfo = aNodeInfoManager->GetNodeInfo(
         aName, nullptr, kNameSpaceID_SVG, nsINode::ELEMENT_NODE);
     MOZ_ASSERT(nodeInfo, "Got null nodeinfo.");
 
-    mozilla::DebugOnly<nsresult> rv =
+    DebugOnly<nsresult> rv =
         aCreator(getter_AddRefs(newElement), nodeInfo.forget(), aFromParser);
     MOZ_ASSERT(NS_SUCCEEDED(rv) && newElement);
   } else {
-    RefPtr<dom::NodeInfo> nodeInfo = aNodeInfoManager->GetNodeInfo(
+    RefPtr<NodeInfo> nodeInfo = aNodeInfoManager->GetNodeInfo(
         aName, nullptr, kNameSpaceID_disabled_SVG, nsINode::ELEMENT_NODE);
     MOZ_ASSERT(nodeInfo, "Got null nodeinfo.");
 
     // The mismatch between NS_NewXMLElement and SVGContentCreatorFunction
     // argument types is annoying.
-    nsCOMPtr<dom::Element> xmlElement;
-    mozilla::DebugOnly<nsresult> rv =
+    nsCOMPtr<Element> xmlElement;
+    DebugOnly<nsresult> rv =
         NS_NewXMLElement(getter_AddRefs(xmlElement), nodeInfo.forget());
     MOZ_ASSERT(NS_SUCCEEDED(rv) && xmlElement);
     newElement = xmlElement;
   }
 
-  dom::Element* newContent = newElement->AsElement();
+  Element* newContent = newElement->AsElement();
   aBuilder->HoldElement(newElement.forget());
 
   if (MOZ_UNLIKELY(aName == nsGkAtoms::style)) {
-    if (auto* linkStyle = dom::LinkStyle::FromNode(*newContent)) {
+    if (auto* linkStyle = LinkStyle::FromNode(*newContent)) {
       linkStyle->DisableUpdates();
     }
   }
@@ -566,26 +564,26 @@ nsIContent* nsHtml5TreeOperation::CreateSVGElement(
 nsIContent* nsHtml5TreeOperation::CreateMathMLElement(
     nsAtom* aName, nsHtml5HtmlAttributes* aAttributes,
     nsNodeInfoManager* aNodeInfoManager, nsHtml5DocumentBuilder* aBuilder) {
-  nsCOMPtr<dom::Element> newElement;
+  nsCOMPtr<Element> newElement;
   if (MOZ_LIKELY(aNodeInfoManager->MathMLEnabled())) {
-    RefPtr<dom::NodeInfo> nodeInfo = aNodeInfoManager->GetNodeInfo(
+    RefPtr<NodeInfo> nodeInfo = aNodeInfoManager->GetNodeInfo(
         aName, nullptr, kNameSpaceID_MathML, nsINode::ELEMENT_NODE);
     NS_ASSERTION(nodeInfo, "Got null nodeinfo.");
 
-    mozilla::DebugOnly<nsresult> rv =
+    DebugOnly<nsresult> rv =
         NS_NewMathMLElement(getter_AddRefs(newElement), nodeInfo.forget());
     MOZ_ASSERT(NS_SUCCEEDED(rv) && newElement);
   } else {
-    RefPtr<dom::NodeInfo> nodeInfo = aNodeInfoManager->GetNodeInfo(
+    RefPtr<NodeInfo> nodeInfo = aNodeInfoManager->GetNodeInfo(
         aName, nullptr, kNameSpaceID_disabled_MathML, nsINode::ELEMENT_NODE);
     NS_ASSERTION(nodeInfo, "Got null nodeinfo.");
 
-    mozilla::DebugOnly<nsresult> rv =
+    DebugOnly<nsresult> rv =
         NS_NewXMLElement(getter_AddRefs(newElement), nodeInfo.forget());
     MOZ_ASSERT(NS_SUCCEEDED(rv) && newElement);
   }
 
-  dom::Element* newContent = newElement;
+  Element* newContent = newElement;
   aBuilder->HoldElement(newElement.forget());
 
   if (!aAttributes) {
@@ -613,8 +611,7 @@ nsIContent* nsHtml5TreeOperation::CreateMathMLElement(
 
 void nsHtml5TreeOperation::SetFormElement(nsIContent* aNode,
                                           nsIContent* aParent) {
-  RefPtr<dom::HTMLFormElement> formElement =
-      dom::HTMLFormElement::FromNodeOrNull(aParent);
+  RefPtr formElement = HTMLFormElement::FromNodeOrNull(aParent);
   NS_ASSERTION(formElement,
                "The form element doesn't implement HTMLFormElement.");
   nsCOMPtr<nsIFormControl> formControl(do_QueryInterface(aNode));
@@ -623,9 +620,8 @@ void nsHtml5TreeOperation::SetFormElement(nsIContent* aNode,
           FormControlType::FormAssociatedCustomElement &&
       !aNode->AsElement()->HasAttr(nsGkAtoms::form)) {
     formControl->SetForm(formElement);
-  } else if (HTMLImageElement* domImageElement =
-                 dom::HTMLImageElement::FromNodeOrNull(aNode)) {
-    domImageElement->SetForm(formElement);
+  } else if (auto* image = HTMLImageElement::FromNodeOrNull(aNode)) {
+    image->SetForm(formElement);
   }
 }
 
@@ -670,8 +666,7 @@ nsresult nsHtml5TreeOperation::AppendComment(nsIContent* aParent,
                                              char16_t* aBuffer, int32_t aLength,
                                              nsHtml5DocumentBuilder* aBuilder) {
   nsNodeInfoManager* nodeInfoManager = aParent->OwnerDoc()->NodeInfoManager();
-  RefPtr<dom::Comment> comment =
-      new (nodeInfoManager) dom::Comment(nodeInfoManager);
+  RefPtr<Comment> comment = new (nodeInfoManager) Comment(nodeInfoManager);
   NS_ASSERTION(comment, "Infallible malloc failed?");
   nsresult rv = comment->SetText(aBuffer, aLength, false);
   NS_ENSURE_SUCCESS(rv, rv);
@@ -681,8 +676,8 @@ nsresult nsHtml5TreeOperation::AppendComment(nsIContent* aParent,
 
 nsresult nsHtml5TreeOperation::AppendCommentToDocument(
     char16_t* aBuffer, int32_t aLength, nsHtml5DocumentBuilder* aBuilder) {
-  RefPtr<dom::Comment> comment = new (aBuilder->GetNodeInfoManager())
-      dom::Comment(aBuilder->GetNodeInfoManager());
+  RefPtr<Comment> comment = new (aBuilder->GetNodeInfoManager())
+      Comment(aBuilder->GetNodeInfoManager());
   NS_ASSERTION(comment, "Infallible malloc failed?");
   nsresult rv = comment->SetText(aBuffer, aLength, false);
   NS_ENSURE_SUCCESS(rv, rv);
@@ -695,7 +690,7 @@ nsresult nsHtml5TreeOperation::AppendDoctypeToDocument(
     nsHtml5DocumentBuilder* aBuilder) {
   // Adapted from nsXMLContentSink
   // Create a new doctype node
-  RefPtr<dom::DocumentType> docType =
+  RefPtr<DocumentType> docType =
       NS_NewDOMDocumentType(aBuilder->GetNodeInfoManager(), aName, aPublicId,
                             aSystemId, VoidString());
   return AppendToDocument(docType, aBuilder);
@@ -703,10 +698,8 @@ nsresult nsHtml5TreeOperation::AppendDoctypeToDocument(
 
 nsIContent* nsHtml5TreeOperation::GetDocumentFragmentForTemplate(
     nsIContent* aNode) {
-  dom::HTMLTemplateElement* tempElem =
-      static_cast<dom::HTMLTemplateElement*>(aNode);
-  RefPtr<dom::DocumentFragment> frag = tempElem->Content();
-  return frag;
+  auto* tempElem = static_cast<HTMLTemplateElement*>(aNode);
+  return tempElem->Content();
 }
 
 nsIContent* nsHtml5TreeOperation::GetFosterParent(nsIContent* aTable,
@@ -808,7 +801,7 @@ nsresult nsHtml5TreeOperation::Perform(nsHtml5TreeOpExecutor* aBuilder,
 
     nsresult operator()(const opCreateHTMLElement& aOperation) {
       nsIContent** target = aOperation.mContent;
-      mozilla::dom::HTMLContentCreatorFunction creator = aOperation.mCreator;
+      HTMLContentCreatorFunction creator = aOperation.mCreator;
       nsAtom* name = aOperation.mName;
       nsHtml5HtmlAttributes* attributes = aOperation.mAttributes;
       nsIContent* intendedParent =
@@ -827,7 +820,7 @@ nsresult nsHtml5TreeOperation::Perform(nsHtml5TreeOpExecutor* aBuilder,
 
     nsresult operator()(const opCreateSVGElement& aOperation) {
       nsIContent** target = aOperation.mContent;
-      mozilla::dom::SVGContentCreatorFunction creator = aOperation.mCreator;
+      SVGContentCreatorFunction creator = aOperation.mCreator;
       nsAtom* name = aOperation.mName;
       nsHtml5HtmlAttributes* attributes = aOperation.mAttributes;
       nsIContent* intendedParent =
@@ -988,7 +981,7 @@ nsresult nsHtml5TreeOperation::Perform(nsHtml5TreeOpExecutor* aBuilder,
 
     nsresult operator()(const opSetStyleLineNumber& aOperation) {
       nsIContent* node = *(aOperation.mContent);
-      if (auto* linkStyle = dom::LinkStyle::FromNode(*node)) {
+      if (auto* linkStyle = LinkStyle::FromNode(*node)) {
         linkStyle->SetLineNumber(aOperation.mLineNumber);
       } else {
         MOZ_ASSERT(nsNameSpaceManager::GetInstance()->mSVGDisabled,