Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1536 insertions, 0 deletions

diff --git a/dom/xml/nsXMLContentSink.cpp b/dom/xml/nsXMLContentSink.cpp
new file mode 100644
index 0000000000..4080a10b93
--- /dev/null
+++ b/dom/xml/nsXMLContentSink.cpp
@@ -0,0 +1,1536 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsCOMPtr.h"
+#include "nsXMLContentSink.h"
+#include "nsIParser.h"
+#include "mozilla/dom/Document.h"
+#include "nsIContent.h"
+#include "nsIURI.h"
+#include "nsNetUtil.h"
+#include "nsHTMLParts.h"
+#include "nsCRT.h"
+#include "mozilla/StyleSheetInlines.h"
+#include "mozilla/css/Loader.h"
+#include "nsGkAtoms.h"
+#include "nsContentUtils.h"
+#include "nsDocElementCreatedNotificationRunner.h"
+#include "nsIDocShell.h"
+#include "nsIScriptContext.h"
+#include "nsNameSpaceManager.h"
+#include "nsIScriptSecurityManager.h"
+#include "nsIContentViewer.h"
+#include "prtime.h"
+#include "mozilla/Logging.h"
+#include "nsRect.h"
+#include "nsIScriptElement.h"
+#include "nsReadableUtils.h"
+#include "nsUnicharUtils.h"
+#include "nsIChannel.h"
+#include "nsXMLPrettyPrinter.h"
+#include "nsNodeInfoManager.h"
+#include "nsContentCreatorFunctions.h"
+#include "nsIContentPolicy.h"
+#include "nsContentPolicyUtils.h"
+#include "nsError.h"
+#include "nsIScriptGlobalObject.h"
+#include "mozAutoDocUpdate.h"
+#include "nsMimeTypes.h"
+#include "nsHtml5SVGLoadDispatcher.h"
+#include "nsTextNode.h"
+#include "mozilla/dom/CDATASection.h"
+#include "mozilla/dom/Comment.h"
+#include "mozilla/dom/DocumentType.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/HTMLTemplateElement.h"
+#include "mozilla/dom/MutationObservers.h"
+#include "mozilla/dom/ProcessingInstruction.h"
+#include "mozilla/dom/ScriptLoader.h"
+#include "mozilla/dom/txMozillaXSLTProcessor.h"
+#include "mozilla/CycleCollectedJSContext.h"
+#include "mozilla/LoadInfo.h"
+#include "mozilla/UseCounter.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+// XXX Open Issues:
+// 1) what's not allowed - We need to figure out which HTML tags
+//    (prefixed with a HTML namespace qualifier) are explicitly not
+//    allowed (if any).
+// 2) factoring code with nsHTMLContentSink - There's some amount of
+//    common code between this and the HTML content sink. This will
+//    increase as we support more and more HTML elements. How can code
+//    from the code be factored?
+
+nsresult NS_NewXMLContentSink(nsIXMLContentSink** aResult, Document* aDoc,
+                              nsIURI* aURI, nsISupports* aContainer,
+                              nsIChannel* aChannel) {
+  MOZ_ASSERT(nullptr != aResult, "null ptr");
+  if (nullptr == aResult) {
+    return NS_ERROR_NULL_POINTER;
+  }
+  RefPtr<nsXMLContentSink> it = new nsXMLContentSink();
+
+  nsresult rv = it->Init(aDoc, aURI, aContainer, aChannel);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  it.forget(aResult);
+  return NS_OK;
+}
+
+nsXMLContentSink::nsXMLContentSink()
+    : mState(eXMLContentSinkState_InProlog),
+      mTextLength(0),
+      mNotifyLevel(0),
+      mPrettyPrintXML(true),
+      mPrettyPrintHasSpecialRoot(0),
+      mPrettyPrintHasFactoredElements(0),
+      mPrettyPrinting(0),
+      mPreventScriptExecution(0) {
+  PodArrayZero(mText);
+}
+
+nsXMLContentSink::~nsXMLContentSink() = default;
+
+nsresult nsXMLContentSink::Init(Document* aDoc, nsIURI* aURI,
+                                nsISupports* aContainer, nsIChannel* aChannel) {
+  nsresult rv = nsContentSink::Init(aDoc, aURI, aContainer, aChannel);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  aDoc->AddObserver(this);
+  mIsDocumentObserver = true;
+
+  if (!mDocShell) {
+    mPrettyPrintXML = false;
+  }
+
+  mState = eXMLContentSinkState_InProlog;
+  mDocElement = nullptr;
+
+  return NS_OK;
+}
+
+inline void ImplCycleCollectionTraverse(
+    nsCycleCollectionTraversalCallback& aCallback,
+    nsXMLContentSink::StackNode& aField, const char* aName,
+    uint32_t aFlags = 0) {
+  ImplCycleCollectionTraverse(aCallback, aField.mContent, aName, aFlags);
+}
+
+inline void ImplCycleCollectionUnlink(nsXMLContentSink::StackNode& aField) {
+  ImplCycleCollectionUnlink(aField.mContent);
+}
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(nsXMLContentSink)
+  NS_INTERFACE_MAP_ENTRY(nsIContentSink)
+  NS_INTERFACE_MAP_ENTRY(nsIXMLContentSink)
+  NS_INTERFACE_MAP_ENTRY(nsIExpatSink)
+  NS_INTERFACE_MAP_ENTRY(nsITransformObserver)
+NS_INTERFACE_MAP_END_INHERITING(nsContentSink)
+
+NS_IMPL_ADDREF_INHERITED(nsXMLContentSink, nsContentSink)
+NS_IMPL_RELEASE_INHERITED(nsXMLContentSink, nsContentSink)
+
+NS_IMPL_CYCLE_COLLECTION_INHERITED(nsXMLContentSink, nsContentSink,
+                                   mCurrentHead, mDocElement, mLastTextNode,
+                                   mContentStack, mDocumentChildren)
+
+// nsIContentSink
+NS_IMETHODIMP
+nsXMLContentSink::WillParse(void) { return WillParseImpl(); }
+
+NS_IMETHODIMP
+nsXMLContentSink::WillBuildModel(nsDTDMode aDTDMode) {
+  WillBuildModelImpl();
+
+  // Notify document that the load is beginning
+  mDocument->BeginLoad();
+
+  // Check for correct load-command for maybe prettyprinting
+  if (mPrettyPrintXML) {
+    nsAutoCString command;
+    GetParser()->GetCommand(command);
+    if (!command.EqualsLiteral("view")) {
+      mPrettyPrintXML = false;
+    }
+  }
+
+  return NS_OK;
+}
+
+bool nsXMLContentSink::CanStillPrettyPrint() {
+  return mPrettyPrintXML &&
+         (!mPrettyPrintHasFactoredElements || mPrettyPrintHasSpecialRoot);
+}
+
+nsresult nsXMLContentSink::MaybePrettyPrint() {
+  if (!CanStillPrettyPrint()) {
+    mPrettyPrintXML = false;
+
+    return NS_OK;
+  }
+
+  {
+    // Try to perform a microtask checkpoint; this avoids always breaking
+    // pretty-printing if webextensions insert new content right after the
+    // document loads.
+    nsAutoMicroTask mt;
+  }
+
+  // stop observing in order to avoid crashing when replacing content
+  mDocument->RemoveObserver(this);
+  mIsDocumentObserver = false;
+
+  // Reenable the CSSLoader so that the prettyprinting stylesheets can load
+  if (mCSSLoader) {
+    mCSSLoader->SetEnabled(true);
+  }
+
+  RefPtr<nsXMLPrettyPrinter> printer;
+  nsresult rv = NS_NewXMLPrettyPrinter(getter_AddRefs(printer));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  bool isPrettyPrinting;
+  rv = printer->PrettyPrint(mDocument, &isPrettyPrinting);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  mPrettyPrinting = isPrettyPrinting;
+  return NS_OK;
+}
+
+static void CheckXSLTParamPI(ProcessingInstruction* aPi,
+                             nsIDocumentTransformer* aProcessor,
+                             nsINode* aSource) {
+  nsAutoString target, data;
+  aPi->GetTarget(target);
+
+  // Check for namespace declarations
+  if (target.EqualsLiteral("xslt-param-namespace")) {
+    aPi->GetData(data);
+    nsAutoString prefix, namespaceAttr;
+    nsContentUtils::GetPseudoAttributeValue(data, nsGkAtoms::prefix, prefix);
+    if (!prefix.IsEmpty() && nsContentUtils::GetPseudoAttributeValue(
+                                 data, nsGkAtoms::_namespace, namespaceAttr)) {
+      aProcessor->AddXSLTParamNamespace(prefix, namespaceAttr);
+    }
+  }
+
+  // Check for actual parameters
+  else if (target.EqualsLiteral("xslt-param")) {
+    aPi->GetData(data);
+    nsAutoString name, namespaceAttr, select, value;
+    nsContentUtils::GetPseudoAttributeValue(data, nsGkAtoms::name, name);
+    nsContentUtils::GetPseudoAttributeValue(data, nsGkAtoms::_namespace,
+                                            namespaceAttr);
+    if (!nsContentUtils::GetPseudoAttributeValue(data, nsGkAtoms::select,
+                                                 select)) {
+      select.SetIsVoid(true);
+    }
+    if (!nsContentUtils::GetPseudoAttributeValue(data, nsGkAtoms::value,
+                                                 value)) {
+      value.SetIsVoid(true);
+    }
+    if (!name.IsEmpty()) {
+      aProcessor->AddXSLTParam(name, namespaceAttr, select, value, aSource);
+    }
+  }
+}
+
+NS_IMETHODIMP
+nsXMLContentSink::DidBuildModel(bool aTerminated) {
+  if (!mParser) {
+    // If mParser is null, this parse has already been terminated and must
+    // not been terminated again. However, Document may still think that
+    // the parse has not been terminated and call back into here in the case
+    // where the XML parser has finished but the XSLT transform associated
+    // with the document has not.
+    return NS_OK;
+  }
+
+  FlushTags();
+
+  DidBuildModelImpl(aTerminated);
+
+  if (mXSLTProcessor) {
+    // stop observing in order to avoid crashing when replacing content
+    mDocument->RemoveObserver(this);
+    mIsDocumentObserver = false;
+
+    ErrorResult rv;
+    RefPtr<DocumentFragment> source = mDocument->CreateDocumentFragment();
+    for (nsIContent* child : mDocumentChildren) {
+      // XPath data model doesn't have DocumentType nodes.
+      if (child->NodeType() != nsINode::DOCUMENT_TYPE_NODE) {
+        source->AppendChild(*child, rv);
+        if (rv.Failed()) {
+          return rv.StealNSResult();
+        }
+      }
+    }
+
+    // Check for xslt-param and xslt-param-namespace PIs
+    for (nsIContent* child : mDocumentChildren) {
+      if (auto pi = ProcessingInstruction::FromNode(child)) {
+        CheckXSLTParamPI(pi, mXSLTProcessor, source);
+      } else if (child->IsElement()) {
+        // Only honor PIs in the prolog
+        break;
+      }
+    }
+
+    mXSLTProcessor->SetSourceContentModel(source);
+    // Since the processor now holds a reference to us we drop our reference
+    // to it to avoid owning cycles
+    mXSLTProcessor = nullptr;
+  } else {
+    // Kick off layout for non-XSLT transformed documents.
+
+    // Check if we want to prettyprint
+    MaybePrettyPrint();
+
+    bool startLayout = true;
+
+    if (mPrettyPrinting) {
+      NS_ASSERTION(!mPendingSheetCount, "Shouldn't have pending sheets here!");
+
+      // We're pretty-printing now.  See whether we should wait up on
+      // stylesheet loads
+      if (mDocument->CSSLoader()->HasPendingLoads()) {
+        mDocument->CSSLoader()->AddObserver(this);
+        // wait for those sheets to load
+        startLayout = false;
+      }
+    }
+
+    if (startLayout) {
+      StartLayout(false);
+
+      ScrollToRef();
+    }
+
+    mDocument->RemoveObserver(this);
+    mIsDocumentObserver = false;
+
+    mDocument->EndLoad();
+
+    DropParserAndPerfHint();
+  }
+
+  return NS_OK;
+}
+
+nsresult nsXMLContentSink::OnDocumentCreated(Document* aSourceDocument,
+                                             Document* aResultDocument) {
+  aResultDocument->SetDocWriteDisabled(true);
+
+  nsCOMPtr<nsIContentViewer> contentViewer;
+  mDocShell->GetContentViewer(getter_AddRefs(contentViewer));
+  // Make sure that we haven't loaded a new document into the contentviewer
+  // after starting the XSLT transform.
+  if (contentViewer && contentViewer->GetDocument() == aSourceDocument) {
+    return contentViewer->SetDocumentInternal(aResultDocument, true);
+  }
+  return NS_OK;
+}
+
+nsresult nsXMLContentSink::OnTransformDone(Document* aSourceDocument,
+                                           nsresult aResult,
+                                           Document* aResultDocument) {
+  MOZ_ASSERT(aResultDocument,
+             "Don't notify about transform end without a document.");
+
+  mDocumentChildren.Clear();
+
+  nsCOMPtr<nsIContentViewer> contentViewer;
+  mDocShell->GetContentViewer(getter_AddRefs(contentViewer));
+
+  RefPtr<Document> originalDocument = mDocument;
+  bool blockingOnload = mIsBlockingOnload;
+
+  // Make sure that we haven't loaded a new document into the contentviewer
+  // after starting the XSLT transform.
+  if (contentViewer && (contentViewer->GetDocument() == aSourceDocument ||
+                        contentViewer->GetDocument() == aResultDocument)) {
+    if (NS_FAILED(aResult)) {
+      // Transform failed.
+      aResultDocument->SetMayStartLayout(false);
+      // We have an error document.
+      contentViewer->SetDocument(aResultDocument);
+    }
+
+    if (!mRunsToCompletion) {
+      // This BlockOnload call corresponds to the UnblockOnload call in
+      // nsContentSink::DropParserAndPerfHint.
+      aResultDocument->BlockOnload();
+      mIsBlockingOnload = true;
+    }
+    // Transform succeeded, or it failed and we have an error document to
+    // display.
+    mDocument = aResultDocument;
+    aResultDocument->SetDocWriteDisabled(false);
+
+    // Notify document observers that all the content has been stuck
+    // into the document.
+    // XXX do we need to notify for things like PIs?  Or just the
+    // documentElement?
+    nsIContent* rootElement = mDocument->GetRootElement();
+    if (rootElement) {
+      NS_ASSERTION(mDocument->ComputeIndexOf(rootElement).isSome(),
+                   "rootElement not in doc?");
+      mDocument->BeginUpdate();
+      MutationObservers::NotifyContentInserted(mDocument, rootElement);
+      mDocument->EndUpdate();
+    }
+
+    // Start the layout process
+    StartLayout(false);
+
+    ScrollToRef();
+  }
+
+  originalDocument->EndLoad();
+  if (blockingOnload) {
+    // This UnblockOnload call corresponds to the BlockOnload call in
+    // nsContentSink::WillBuildModelImpl.
+    originalDocument->UnblockOnload(true);
+  }
+
+  DropParserAndPerfHint();
+
+  // By this point, the result document has been set in the content viewer.  But
+  // the content viewer does not call Destroy on the original document, so we
+  // won't end up reporting document use counters.  It's possible we should be
+  // detaching the document from the window, but for now, we call
+  // ReportDocumentUseCounters on the original document here, to avoid
+  // assertions in ~Document about not having reported them.
+  originalDocument->ReportDocumentUseCounters();
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXMLContentSink::StyleSheetLoaded(StyleSheet* aSheet, bool aWasDeferred,
+                                   nsresult aStatus) {
+  if (!mPrettyPrinting) {
+    return nsContentSink::StyleSheetLoaded(aSheet, aWasDeferred, aStatus);
+  }
+
+  if (!mDocument->CSSLoader()->HasPendingLoads()) {
+    mDocument->CSSLoader()->RemoveObserver(this);
+    StartLayout(false);
+    ScrollToRef();
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsXMLContentSink::WillInterrupt(void) { return WillInterruptImpl(); }
+
+void nsXMLContentSink::WillResume() { WillResumeImpl(); }
+
+NS_IMETHODIMP
+nsXMLContentSink::SetParser(nsParserBase* aParser) {
+  MOZ_ASSERT(aParser, "Should have a parser here!");
+  mParser = aParser;
+  return NS_OK;
+}
+
+static bool FindIsAttrValue(const char16_t** aAtts, const char16_t** aResult) {
+  RefPtr<nsAtom> prefix, localName;
+  for (; *aAtts; aAtts += 2) {
+    int32_t nameSpaceID;
+    nsContentUtils::SplitExpatName(aAtts[0], getter_AddRefs(prefix),
+                                   getter_AddRefs(localName), &nameSpaceID);
+    if (nameSpaceID == kNameSpaceID_None && localName == nsGkAtoms::is) {
+      *aResult = aAtts[1];
+
+      return true;
+    }
+  }
+
+  return false;
+}
+
+nsresult nsXMLContentSink::CreateElement(
+    const char16_t** aAtts, uint32_t aAttsCount,
+    mozilla::dom::NodeInfo* aNodeInfo, uint32_t aLineNumber,
+    uint32_t aColumnNumber, nsIContent** aResult, bool* aAppendContent,
+    FromParser aFromParser) {
+  NS_ASSERTION(aNodeInfo, "can't create element without nodeinfo");
+
+  *aResult = nullptr;
+  *aAppendContent = true;
+  nsresult rv = NS_OK;
+
+  RefPtr<mozilla::dom::NodeInfo> ni = aNodeInfo;
+  RefPtr<Element> content;
+
+  const char16_t* is = nullptr;
+  if ((aNodeInfo->NamespaceEquals(kNameSpaceID_XHTML) ||
+       aNodeInfo->NamespaceEquals(kNameSpaceID_XUL)) &&
+      FindIsAttrValue(aAtts, &is)) {
+    const nsDependentString isStr(is);
+    rv = NS_NewElement(getter_AddRefs(content), ni.forget(), aFromParser,
+                       &isStr);
+  } else {
+    rv = NS_NewElement(getter_AddRefs(content), ni.forget(), aFromParser);
+  }
+
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (aNodeInfo->Equals(nsGkAtoms::script, kNameSpaceID_XHTML) ||
+      aNodeInfo->Equals(nsGkAtoms::script, kNameSpaceID_SVG)) {
+    nsCOMPtr<nsIScriptElement> sele = do_QueryInterface(content);
+    if (sele) {
+      sele->SetScriptLineNumber(aLineNumber);
+      sele->SetScriptColumnNumber(aColumnNumber);
+      sele->SetCreatorParser(GetParser());
+    } else {
+      MOZ_ASSERT(nsNameSpaceManager::GetInstance()->mSVGDisabled,
+                 "Node didn't QI to script, but SVG wasn't disabled.");
+    }
+  }
+
+  // XHTML needs some special attention
+  if (aNodeInfo->NamespaceEquals(kNameSpaceID_XHTML)) {
+    mPrettyPrintHasFactoredElements = true;
+  } else {
+    // If we care, find out if we just used a special factory.
+    if (!mPrettyPrintHasFactoredElements && !mPrettyPrintHasSpecialRoot &&
+        mPrettyPrintXML) {
+      mPrettyPrintHasFactoredElements =
+          nsNameSpaceManager::GetInstance()->HasElementCreator(
+              aNodeInfo->NamespaceID());
+    }
+
+    if (!aNodeInfo->NamespaceEquals(kNameSpaceID_SVG)) {
+      content.forget(aResult);
+
+      return NS_OK;
+    }
+  }
+
+  if (aNodeInfo->Equals(nsGkAtoms::link, kNameSpaceID_XHTML) ||
+      aNodeInfo->Equals(nsGkAtoms::style, kNameSpaceID_XHTML) ||
+      aNodeInfo->Equals(nsGkAtoms::style, kNameSpaceID_SVG)) {
+    if (auto* linkStyle = LinkStyle::FromNode(*content)) {
+      if (aFromParser) {
+        linkStyle->SetEnableUpdates(false);
+      }
+      if (!aNodeInfo->Equals(nsGkAtoms::link, kNameSpaceID_XHTML)) {
+        linkStyle->SetLineNumber(aFromParser ? aLineNumber : 0);
+        linkStyle->SetColumnNumber(aFromParser ? aColumnNumber : 0);
+      }
+    }
+  }
+
+  content.forget(aResult);
+
+  return NS_OK;
+}
+
+nsresult nsXMLContentSink::CloseElement(nsIContent* aContent) {
+  NS_ASSERTION(aContent, "missing element to close");
+
+  mozilla::dom::NodeInfo* nodeInfo = aContent->NodeInfo();
+
+  // Some HTML nodes need DoneAddingChildren() called to initialize
+  // properly (eg form state restoration).
+  if (nsIContent::RequiresDoneAddingChildren(nodeInfo->NamespaceID(),
+                                             nodeInfo->NameAtom())) {
+    aContent->DoneAddingChildren(HaveNotifiedForCurrentContent());
+  }
+
+  if (IsMonolithicContainer(nodeInfo)) {
+    mInMonolithicContainer--;
+  }
+
+  if (!nodeInfo->NamespaceEquals(kNameSpaceID_XHTML) &&
+      !nodeInfo->NamespaceEquals(kNameSpaceID_SVG)) {
+    return NS_OK;
+  }
+
+  if (nodeInfo->Equals(nsGkAtoms::script, kNameSpaceID_XHTML) ||
+      nodeInfo->Equals(nsGkAtoms::script, kNameSpaceID_SVG)) {
+    nsCOMPtr<nsIScriptElement> sele = do_QueryInterface(aContent);
+    if (!sele) {
+      MOZ_ASSERT(nsNameSpaceManager::GetInstance()->mSVGDisabled,
+                 "Node didn't QI to script, but SVG wasn't disabled.");
+      return NS_OK;
+    }
+
+    if (mPreventScriptExecution) {
+      sele->PreventExecution();
+      return NS_OK;
+    }
+
+    // Always check the clock in nsContentSink right after a script
+    StopDeflecting();
+
+    // Now tell the script that it's ready to go. This may execute the script
+    // or return true, or neither if the script doesn't need executing.
+    bool block = sele->AttemptToExecute();
+    if (mParser) {
+      if (block) {
+        GetParser()->BlockParser();
+      }
+
+      // If the parser got blocked, make sure to return the appropriate rv.
+      // I'm not sure if this is actually needed or not.
+      if (!mParser->IsParserEnabled()) {
+        block = true;
+      }
+    }
+
+    return block ? NS_ERROR_HTMLPARSER_BLOCK : NS_OK;
+  }
+
+  nsresult rv = NS_OK;
+  if (nodeInfo->Equals(nsGkAtoms::link, kNameSpaceID_XHTML) ||
+      nodeInfo->Equals(nsGkAtoms::style, kNameSpaceID_XHTML) ||
+      nodeInfo->Equals(nsGkAtoms::style, kNameSpaceID_SVG)) {
+    if (auto* linkStyle = LinkStyle::FromNode(*aContent)) {
+      linkStyle->SetEnableUpdates(true);
+      auto updateOrError =
+          linkStyle->UpdateStyleSheet(mRunsToCompletion ? nullptr : this);
+      if (updateOrError.isErr()) {
+        rv = updateOrError.unwrapErr();
+      } else if (updateOrError.unwrap().ShouldBlock() && !mRunsToCompletion) {
+        ++mPendingSheetCount;
+        mScriptLoader->AddParserBlockingScriptExecutionBlocker();
+      }
+    }
+  }
+
+  return rv;
+}
+
+nsresult nsXMLContentSink::AddContentAsLeaf(nsIContent* aContent) {
+  nsresult result = NS_OK;
+
+  if (mState == eXMLContentSinkState_InProlog) {
+    NS_ASSERTION(mDocument, "Fragments have no prolog");
+    mDocumentChildren.AppendElement(aContent);
+  } else if (mState == eXMLContentSinkState_InEpilog) {
+    NS_ASSERTION(mDocument, "Fragments have no epilog");
+    if (mXSLTProcessor) {
+      mDocumentChildren.AppendElement(aContent);
+    } else {
+      mDocument->AppendChildTo(aContent, false, IgnoreErrors());
+    }
+  } else {
+    nsCOMPtr<nsIContent> parent = GetCurrentContent();
+
+    if (parent) {
+      ErrorResult rv;
+      parent->AppendChildTo(aContent, false, rv);
+      result = rv.StealNSResult();
+    }
+  }
+  return result;
+}
+
+// Create an XML parser and an XSL content sink and start parsing
+// the XSL stylesheet located at the given URI.
+nsresult nsXMLContentSink::LoadXSLStyleSheet(nsIURI* aUrl) {
+  nsCOMPtr<nsIDocumentTransformer> processor = new txMozillaXSLTProcessor();
+  mDocument->SetUseCounter(eUseCounter_custom_XSLStylesheet);
+
+  processor->SetTransformObserver(this);
+
+  if (NS_SUCCEEDED(processor->LoadStyleSheet(aUrl, mDocument))) {
+    mXSLTProcessor.swap(processor);
+  }
+
+  // Intentionally ignore errors here, we should continue loading the
+  // XML document whether we're able to load the XSLT stylesheet or
+  // not.
+
+  return NS_OK;
+}
+
+nsresult nsXMLContentSink::ProcessStyleLinkFromHeader(
+    const nsAString& aHref, bool aAlternate, const nsAString& aTitle,
+    const nsAString& aIntegrity, const nsAString& aType,
+    const nsAString& aMedia, const nsAString& aReferrerPolicy) {
+  mPrettyPrintXML = false;
+
+  nsAutoCString cmd;
+  if (mParser) GetParser()->GetCommand(cmd);
+  if (cmd.EqualsASCII(kLoadAsData))
+    return NS_OK;  // Do not load stylesheets when loading as data
+
+  bool wasXSLT;
+  nsresult rv = MaybeProcessXSLTLink(nullptr, aHref, aAlternate, aType, aType,
+                                     aMedia, aReferrerPolicy, &wasXSLT);
+  NS_ENSURE_SUCCESS(rv, rv);
+  if (wasXSLT) {
+    // We're done here.
+    return NS_OK;
+  }
+
+  // Otherwise fall through to nsContentSink to handle CSS Link headers.
+  return nsContentSink::ProcessStyleLinkFromHeader(
+      aHref, aAlternate, aTitle, aIntegrity, aType, aMedia, aReferrerPolicy);
+}
+
+nsresult nsXMLContentSink::MaybeProcessXSLTLink(
+    ProcessingInstruction* aProcessingInstruction, const nsAString& aHref,
+    bool aAlternate, const nsAString& aTitle, const nsAString& aType,
+    const nsAString& aMedia, const nsAString& aReferrerPolicy, bool* aWasXSLT) {
+  bool wasXSLT = aType.LowerCaseEqualsLiteral(TEXT_XSL) ||
+                 aType.LowerCaseEqualsLiteral(APPLICATION_XSLT_XML) ||
+                 aType.LowerCaseEqualsLiteral(TEXT_XML) ||
+                 aType.LowerCaseEqualsLiteral(APPLICATION_XML);
+
+  if (aWasXSLT) {
+    *aWasXSLT = wasXSLT;
+  }
+
+  if (!wasXSLT) {
+    return NS_OK;
+  }
+
+  if (aAlternate) {
+    // don't load alternate XSLT
+    return NS_OK;
+  }
+  // LoadXSLStyleSheet needs a mDocShell.
+  if (!mDocShell) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIURI> url;
+  nsresult rv = NS_NewURI(getter_AddRefs(url), aHref, nullptr,
+                          mDocument->GetDocBaseURI());
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Do security check
+  nsIScriptSecurityManager* secMan = nsContentUtils::GetSecurityManager();
+  rv = secMan->CheckLoadURIWithPrincipal(mDocument->NodePrincipal(), url,
+                                         nsIScriptSecurityManager::ALLOW_CHROME,
+                                         mDocument->InnerWindowID());
+  NS_ENSURE_SUCCESS(rv, NS_OK);
+
+  nsCOMPtr<nsILoadInfo> secCheckLoadInfo =
+      new net::LoadInfo(mDocument->NodePrincipal(),  // loading principal
+                        mDocument->NodePrincipal(),  // triggering principal
+                        aProcessingInstruction,
+                        nsILoadInfo::SEC_ONLY_FOR_EXPLICIT_CONTENTSEC_CHECK,
+                        nsIContentPolicy::TYPE_XSLT);
+
+  // Do content policy check
+  int16_t decision = nsIContentPolicy::ACCEPT;
+  rv = NS_CheckContentLoadPolicy(url, secCheckLoadInfo,
+                                 NS_ConvertUTF16toUTF8(aType), &decision,
+                                 nsContentUtils::GetContentPolicy());
+
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (NS_CP_REJECTED(decision)) {
+    return NS_OK;
+  }
+
+  return LoadXSLStyleSheet(url);
+}
+
+void nsXMLContentSink::SetDocumentCharset(NotNull<const Encoding*> aEncoding) {
+  if (mDocument) {
+    mDocument->SetDocumentCharacterSet(aEncoding);
+  }
+}
+
+nsISupports* nsXMLContentSink::GetTarget() { return ToSupports(mDocument); }
+
+bool nsXMLContentSink::IsScriptExecuting() { return IsScriptExecutingImpl(); }
+
+nsresult nsXMLContentSink::FlushText(bool aReleaseTextNode) {
+  nsresult rv = NS_OK;
+
+  if (mTextLength != 0) {
+    if (mLastTextNode) {
+      bool notify = HaveNotifiedForCurrentContent();
+      // We could probably always increase mInNotification here since
+      // if AppendText doesn't notify it shouldn't trigger evil code.
+      // But just in case it does, we don't want to mask any notifications.
+      if (notify) {
+        ++mInNotification;
+      }
+      rv = mLastTextNode->AppendText(mText, mTextLength, notify);
+      if (notify) {
+        --mInNotification;
+      }
+
+      mTextLength = 0;
+    } else {
+      RefPtr<nsTextNode> textContent =
+          new (mNodeInfoManager) nsTextNode(mNodeInfoManager);
+
+      mLastTextNode = textContent;
+
+      // Set the text in the text node
+      textContent->SetText(mText, mTextLength, false);
+      mTextLength = 0;
+
+      // Add text to its parent
+      rv = AddContentAsLeaf(textContent);
+    }
+  }
+
+  if (aReleaseTextNode) {
+    mLastTextNode = nullptr;
+  }
+
+  return rv;
+}
+
+nsIContent* nsXMLContentSink::GetCurrentContent() {
+  if (mContentStack.Length() == 0) {
+    return nullptr;
+  }
+  return GetCurrentStackNode()->mContent;
+}
+
+nsXMLContentSink::StackNode* nsXMLContentSink::GetCurrentStackNode() {
+  int32_t count = mContentStack.Length();
+  return count != 0 ? &mContentStack[count - 1] : nullptr;
+}
+
+nsresult nsXMLContentSink::PushContent(nsIContent* aContent) {
+  MOZ_ASSERT(aContent, "Null content being pushed!");
+  StackNode* sn = mContentStack.AppendElement();
+  NS_ENSURE_TRUE(sn, NS_ERROR_OUT_OF_MEMORY);
+
+  nsIContent* contentToPush = aContent;
+
+  // When an XML parser would append a node to a template element, it
+  // must instead append it to the template element's template contents.
+  if (contentToPush->IsHTMLElement(nsGkAtoms::_template)) {
+    HTMLTemplateElement* templateElement =
+        static_cast<HTMLTemplateElement*>(contentToPush);
+    contentToPush = templateElement->Content();
+  }
+
+  sn->mContent = contentToPush;
+  sn->mNumFlushed = 0;
+  return NS_OK;
+}
+
+void nsXMLContentSink::PopContent() {
+  if (mContentStack.IsEmpty()) {
+    NS_WARNING("Popping empty stack");
+    return;
+  }
+
+  mContentStack.RemoveLastElement();
+}
+
+bool nsXMLContentSink::HaveNotifiedForCurrentContent() const {
+  uint32_t stackLength = mContentStack.Length();
+  if (stackLength) {
+    const StackNode& stackNode = mContentStack[stackLength - 1];
+    nsIContent* parent = stackNode.mContent;
+    return stackNode.mNumFlushed == parent->GetChildCount();
+  }
+  return true;
+}
+
+void nsXMLContentSink::MaybeStartLayout(bool aIgnorePendingSheets) {
+  // XXXbz if aIgnorePendingSheets is true, what should we do when
+  // mXSLTProcessor or CanStillPrettyPrint()?
+  if (mLayoutStarted || mXSLTProcessor || CanStillPrettyPrint()) {
+    return;
+  }
+  StartLayout(aIgnorePendingSheets);
+}
+
+////////////////////////////////////////////////////////////////////////
+
+bool nsXMLContentSink::SetDocElement(int32_t aNameSpaceID, nsAtom* aTagName,
+                                     nsIContent* aContent) {
+  if (mDocElement) return false;
+
+  mDocElement = aContent;
+
+  if (mXSLTProcessor) {
+    mDocumentChildren.AppendElement(aContent);
+    return true;
+  }
+
+  if (!mDocumentChildren.IsEmpty()) {
+    for (nsIContent* child : mDocumentChildren) {
+      mDocument->AppendChildTo(child, false, IgnoreErrors());
+    }
+    mDocumentChildren.Clear();
+  }
+
+  // check for root elements that needs special handling for
+  // prettyprinting
+  if (aNameSpaceID == kNameSpaceID_XSLT &&
+      (aTagName == nsGkAtoms::stylesheet || aTagName == nsGkAtoms::transform)) {
+    mPrettyPrintHasSpecialRoot = true;
+    if (mPrettyPrintXML) {
+      // In this case, disable script execution, stylesheet
+      // loading, and auto XLinks since we plan to prettyprint.
+      mDocument->ScriptLoader()->SetEnabled(false);
+      if (mCSSLoader) {
+        mCSSLoader->SetEnabled(false);
+      }
+    }
+  }
+
+  IgnoredErrorResult rv;
+  mDocument->AppendChildTo(mDocElement, NotifyForDocElement(), rv);
+  if (rv.Failed()) {
+    // If we return false here, the caller will bail out because it won't
+    // find a parent content node to append to, which is fine.
+    return false;
+  }
+
+  return true;
+}
+
+NS_IMETHODIMP
+nsXMLContentSink::HandleStartElement(const char16_t* aName,
+                                     const char16_t** aAtts,
+                                     uint32_t aAttsCount, uint32_t aLineNumber,
+                                     uint32_t aColumnNumber) {
+  return HandleStartElement(aName, aAtts, aAttsCount, aLineNumber,
+                            aColumnNumber, true);
+}
+
+nsresult nsXMLContentSink::HandleStartElement(
+    const char16_t* aName, const char16_t** aAtts, uint32_t aAttsCount,
+    uint32_t aLineNumber, uint32_t aColumnNumber, bool aInterruptable) {
+  MOZ_ASSERT(aAttsCount % 2 == 0, "incorrect aAttsCount");
+  // Adjust aAttsCount so it's the actual number of attributes
+  aAttsCount /= 2;
+
+  nsresult result = NS_OK;
+  bool appendContent = true;
+  nsCOMPtr<nsIContent> content;
+
+  // XXX Hopefully the parser will flag this before we get
+  // here. If we're in the epilog, there should be no
+  // new elements
+  MOZ_ASSERT(eXMLContentSinkState_InEpilog != mState);
+
+  FlushText();
+  DidAddContent();
+
+  mState = eXMLContentSinkState_InDocumentElement;
+
+  int32_t nameSpaceID;
+  RefPtr<nsAtom> prefix, localName;
+  nsContentUtils::SplitExpatName(aName, getter_AddRefs(prefix),
+                                 getter_AddRefs(localName), &nameSpaceID);
+
+  if (!OnOpenContainer(aAtts, aAttsCount, nameSpaceID, localName,
+                       aLineNumber)) {
+    return NS_OK;
+  }
+
+  RefPtr<mozilla::dom::NodeInfo> nodeInfo;
+  nodeInfo = mNodeInfoManager->GetNodeInfo(localName, prefix, nameSpaceID,
+                                           nsINode::ELEMENT_NODE);
+
+  result = CreateElement(aAtts, aAttsCount, nodeInfo, aLineNumber,
+                         aColumnNumber, getter_AddRefs(content), &appendContent,
+                         FROM_PARSER_NETWORK);
+  NS_ENSURE_SUCCESS(result, result);
+
+  // Have to do this before we push the new content on the stack... and have to
+  // do that before we set attributes, call BindToTree, etc.  Ideally we'd push
+  // on the stack inside CreateElement (which is effectively what the HTML sink
+  // does), but that's hard with all the subclass overrides going on.
+  nsCOMPtr<nsIContent> parent = GetCurrentContent();
+
+  result = PushContent(content);
+  NS_ENSURE_SUCCESS(result, result);
+
+  // Set the attributes on the new content element
+  result = AddAttributes(aAtts, content->AsElement());
+
+  if (NS_OK == result) {
+    // Store the element
+    if (!SetDocElement(nameSpaceID, localName, content) && appendContent) {
+      NS_ENSURE_TRUE(parent, NS_ERROR_UNEXPECTED);
+
+      parent->AppendChildTo(content, false, IgnoreErrors());
+    }
+  }
+
+  // Some HTML nodes need DoneCreatingElement() called to initialize
+  // properly (eg form state restoration).
+  if (nsIContent::RequiresDoneCreatingElement(nodeInfo->NamespaceID(),
+                                              nodeInfo->NameAtom())) {
+    content->DoneCreatingElement();
+  }
+
+  if (nodeInfo->NamespaceID() == kNameSpaceID_XHTML &&
+      nodeInfo->NameAtom() == nsGkAtoms::head && !mCurrentHead) {
+    mCurrentHead = content;
+  }
+
+  if (IsMonolithicContainer(nodeInfo)) {
+    mInMonolithicContainer++;
+  }
+
+  if (!mXSLTProcessor) {
+    if (content == mDocElement) {
+      nsContentUtils::AddScriptRunner(
+          new nsDocElementCreatedNotificationRunner(mDocument));
+
+      if (aInterruptable && NS_SUCCEEDED(result) && mParser &&
+          !mParser->IsParserEnabled()) {
+        return NS_ERROR_HTMLPARSER_BLOCK;
+      }
+    } else if (!mCurrentHead) {
+      // This isn't the root and we're not inside an XHTML <head>.
+      // Might need to start layout
+      MaybeStartLayout(false);
+    }
+  }
+
+  return aInterruptable && NS_SUCCEEDED(result) ? DidProcessATokenImpl()
+                                                : result;
+}
+
+NS_IMETHODIMP
+nsXMLContentSink::HandleEndElement(const char16_t* aName) {
+  return HandleEndElement(aName, true);
+}
+
+nsresult nsXMLContentSink::HandleEndElement(const char16_t* aName,
+                                            bool aInterruptable) {
+  nsresult result = NS_OK;
+
+  // XXX Hopefully the parser will flag this before we get
+  // here. If we're in the prolog or epilog, there should be
+  // no close tags for elements.
+  MOZ_ASSERT(eXMLContentSinkState_InDocumentElement == mState);
+
+  FlushText();
+
+  StackNode* sn = GetCurrentStackNode();
+  if (!sn) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  nsCOMPtr<nsIContent> content;
+  sn->mContent.swap(content);
+  uint32_t numFlushed = sn->mNumFlushed;
+
+  PopContent();
+  NS_ASSERTION(content, "failed to pop content");
+#ifdef DEBUG
+  // Check that we're closing the right thing
+  RefPtr<nsAtom> debugNameSpacePrefix, debugTagAtom;
+  int32_t debugNameSpaceID;
+  nsContentUtils::SplitExpatName(aName, getter_AddRefs(debugNameSpacePrefix),
+                                 getter_AddRefs(debugTagAtom),
+                                 &debugNameSpaceID);
+  // Check if we are closing a template element because template
+  // elements do not get pushed on the stack, the template
+  // element content is pushed instead.
+  bool isTemplateElement = debugTagAtom == nsGkAtoms::_template &&
+                           debugNameSpaceID == kNameSpaceID_XHTML;
+  NS_ASSERTION(
+      content->NodeInfo()->Equals(debugTagAtom, debugNameSpaceID) ||
+          (debugNameSpaceID == kNameSpaceID_MathML &&
+           content->NodeInfo()->NamespaceID() == kNameSpaceID_disabled_MathML &&
+           content->NodeInfo()->Equals(debugTagAtom)) ||
+          (debugNameSpaceID == kNameSpaceID_SVG &&
+           content->NodeInfo()->NamespaceID() == kNameSpaceID_disabled_SVG &&
+           content->NodeInfo()->Equals(debugTagAtom)) ||
+          isTemplateElement,
+      "Wrong element being closed");
+#endif
+
+  // Make sure to notify on our kids before we call out to any other code that
+  // might reenter us and call FlushTags, in a state in which we've already
+  // popped "content" from the stack but haven't notified on its kids yet.
+  int32_t stackLen = mContentStack.Length();
+  if (mNotifyLevel >= stackLen) {
+    if (numFlushed < content->GetChildCount()) {
+      NotifyAppend(content, numFlushed);
+    }
+    mNotifyLevel = stackLen - 1;
+  }
+
+  result = CloseElement(content);
+
+  if (mCurrentHead == content) {
+    mCurrentHead = nullptr;
+  }
+
+  if (mDocElement == content) {
+    // XXXbz for roots that don't want to be appended on open, we
+    // probably need to deal here.... (and stop appending them on open).
+    mState = eXMLContentSinkState_InEpilog;
+
+    mDocument->OnParsingCompleted();
+
+    // We might have had no occasion to start layout yet.  Do so now.
+    MaybeStartLayout(false);
+  }
+
+  DidAddContent();
+
+  if (content->IsSVGElement(nsGkAtoms::svg)) {
+    FlushTags();
+    nsCOMPtr<nsIRunnable> event = new nsHtml5SVGLoadDispatcher(content);
+    if (NS_FAILED(content->OwnerDoc()->Dispatch(TaskCategory::Other,
+                                                event.forget()))) {
+      NS_WARNING("failed to dispatch svg load dispatcher");
+    }
+  }
+
+  return aInterruptable && NS_SUCCEEDED(result) ? DidProcessATokenImpl()
+                                                : result;
+}
+
+NS_IMETHODIMP
+nsXMLContentSink::HandleComment(const char16_t* aName) {
+  FlushText();
+
+  RefPtr<Comment> comment = new (mNodeInfoManager) Comment(mNodeInfoManager);
+  comment->SetText(nsDependentString(aName), false);
+  nsresult rv = AddContentAsLeaf(comment);
+  DidAddContent();
+
+  return NS_SUCCEEDED(rv) ? DidProcessATokenImpl() : rv;
+}
+
+NS_IMETHODIMP
+nsXMLContentSink::HandleCDataSection(const char16_t* aData, uint32_t aLength) {
+  // XSLT doesn't differentiate between text and cdata and wants adjacent
+  // textnodes merged, so add as text.
+  if (mXSLTProcessor) {
+    return AddText(aData, aLength);
+  }
+
+  FlushText();
+
+  RefPtr<CDATASection> cdata =
+      new (mNodeInfoManager) CDATASection(mNodeInfoManager);
+  cdata->SetText(aData, aLength, false);
+  nsresult rv = AddContentAsLeaf(cdata);
+  DidAddContent();
+
+  return NS_SUCCEEDED(rv) ? DidProcessATokenImpl() : rv;
+}
+
+NS_IMETHODIMP
+nsXMLContentSink::HandleDoctypeDecl(const nsAString& aSubset,
+                                    const nsAString& aName,
+                                    const nsAString& aSystemId,
+                                    const nsAString& aPublicId,
+                                    nsISupports* aCatalogData) {
+  FlushText();
+
+  NS_ASSERTION(mDocument, "Shouldn't get here from a document fragment");
+
+  RefPtr<nsAtom> name = NS_Atomize(aName);
+  NS_ENSURE_TRUE(name, NS_ERROR_OUT_OF_MEMORY);
+
+  // Create a new doctype node
+  RefPtr<DocumentType> docType = NS_NewDOMDocumentType(
+      mNodeInfoManager, name, aPublicId, aSystemId, aSubset);
+
+  MOZ_ASSERT(!aCatalogData,
+             "Need to add back support for catalog style "
+             "sheets");
+
+  mDocumentChildren.AppendElement(docType);
+  DidAddContent();
+  return DidProcessATokenImpl();
+}
+
+NS_IMETHODIMP
+nsXMLContentSink::HandleCharacterData(const char16_t* aData, uint32_t aLength) {
+  return HandleCharacterData(aData, aLength, true);
+}
+
+nsresult nsXMLContentSink::HandleCharacterData(const char16_t* aData,
+                                               uint32_t aLength,
+                                               bool aInterruptable) {
+  nsresult rv = NS_OK;
+  if (aData && mState != eXMLContentSinkState_InProlog &&
+      mState != eXMLContentSinkState_InEpilog) {
+    rv = AddText(aData, aLength);
+  }
+  return aInterruptable && NS_SUCCEEDED(rv) ? DidProcessATokenImpl() : rv;
+}
+
+NS_IMETHODIMP
+nsXMLContentSink::HandleProcessingInstruction(const char16_t* aTarget,
+                                              const char16_t* aData) {
+  FlushText();
+
+  const nsDependentString target(aTarget);
+  const nsDependentString data(aData);
+
+  RefPtr<ProcessingInstruction> node =
+      NS_NewXMLProcessingInstruction(mNodeInfoManager, target, data);
+
+  auto* linkStyle = LinkStyle::FromNode(*node);
+  if (linkStyle) {
+    linkStyle->SetEnableUpdates(false);
+    mPrettyPrintXML = false;
+  }
+
+  nsresult rv = AddContentAsLeaf(node);
+  NS_ENSURE_SUCCESS(rv, rv);
+  DidAddContent();
+
+  if (linkStyle) {
+    // This is an xml-stylesheet processing instruction... but it might not be
+    // a CSS one if the type is set to something else.
+    linkStyle->SetEnableUpdates(true);
+    auto updateOrError =
+        linkStyle->UpdateStyleSheet(mRunsToCompletion ? nullptr : this);
+    if (updateOrError.isErr()) {
+      return updateOrError.unwrapErr();
+    }
+
+    auto update = updateOrError.unwrap();
+    if (update.WillNotify()) {
+      // Successfully started a stylesheet load
+      if (update.ShouldBlock() && !mRunsToCompletion) {
+        ++mPendingSheetCount;
+        mScriptLoader->AddParserBlockingScriptExecutionBlocker();
+      }
+      return NS_OK;
+    }
+  }
+
+  // Check whether this is a CSS stylesheet PI.  Make sure the type
+  // handling here matches
+  // XMLStylesheetProcessingInstruction::GetStyleSheetInfo.
+  nsAutoString type;
+  nsContentUtils::GetPseudoAttributeValue(data, nsGkAtoms::type, type);
+  nsAutoString mimeType, notUsed;
+  nsContentUtils::SplitMimeType(type, mimeType, notUsed);
+
+  if (mState != eXMLContentSinkState_InProlog ||
+      !target.EqualsLiteral("xml-stylesheet") || mimeType.IsEmpty() ||
+      mimeType.LowerCaseEqualsLiteral("text/css")) {
+    // Either not a useful stylesheet PI, or a CSS stylesheet PI that
+    // got handled above by the "ssle" bits.  We're done here.
+    return DidProcessATokenImpl();
+  }
+
+  // If it's not a CSS stylesheet PI...
+  nsAutoString href, title, media;
+  bool isAlternate = false;
+
+  // If there was no href, we can't do anything with this PI
+  if (!ParsePIData(data, href, title, media, isAlternate)) {
+    return DidProcessATokenImpl();
+  }
+
+  // <?xml-stylesheet?> processing instructions don't have a referrerpolicy
+  // pseudo-attribute, so we pass in an empty string
+  rv =
+      MaybeProcessXSLTLink(node, href, isAlternate, title, type, media, u""_ns);
+  return NS_SUCCEEDED(rv) ? DidProcessATokenImpl() : rv;
+}
+
+/* static */
+bool nsXMLContentSink::ParsePIData(const nsString& aData, nsString& aHref,
+                                   nsString& aTitle, nsString& aMedia,
+                                   bool& aIsAlternate) {
+  // If there was no href, we can't do anything with this PI
+  if (!nsContentUtils::GetPseudoAttributeValue(aData, nsGkAtoms::href, aHref)) {
+    return false;
+  }
+
+  nsContentUtils::GetPseudoAttributeValue(aData, nsGkAtoms::title, aTitle);
+
+  nsContentUtils::GetPseudoAttributeValue(aData, nsGkAtoms::media, aMedia);
+
+  nsAutoString alternate;
+  nsContentUtils::GetPseudoAttributeValue(aData, nsGkAtoms::alternate,
+                                          alternate);
+
+  aIsAlternate = alternate.EqualsLiteral("yes");
+
+  return true;
+}
+
+NS_IMETHODIMP
+nsXMLContentSink::HandleXMLDeclaration(const char16_t* aVersion,
+                                       const char16_t* aEncoding,
+                                       int32_t aStandalone) {
+  mDocument->SetXMLDeclaration(aVersion, aEncoding, aStandalone);
+
+  return DidProcessATokenImpl();
+}
+
+NS_IMETHODIMP
+nsXMLContentSink::ReportError(const char16_t* aErrorText,
+                              const char16_t* aSourceText,
+                              nsIScriptError* aError, bool* _retval) {
+  MOZ_ASSERT(aError && aSourceText && aErrorText, "Check arguments!!!");
+  nsresult rv = NS_OK;
+
+  // The expat driver should report the error.  We're just cleaning up the mess.
+  *_retval = true;
+
+  mPrettyPrintXML = false;
+
+  mState = eXMLContentSinkState_InProlog;
+
+  // XXX need to stop scripts here -- hsivonen
+
+  // stop observing in order to avoid crashing when removing content
+  mDocument->RemoveObserver(this);
+  mIsDocumentObserver = false;
+
+  // Clear the current content
+  mDocumentChildren.Clear();
+  while (mDocument->GetLastChild()) {
+    mDocument->GetLastChild()->Remove();
+  }
+  mDocElement = nullptr;
+
+  // Clear any buffered-up text we have.  It's enough to set the length to 0.
+  // The buffer itself is allocated when we're created and deleted in our
+  // destructor, so don't mess with it.
+  mTextLength = 0;
+
+  if (mXSLTProcessor) {
+    // Get rid of the XSLT processor.
+    mXSLTProcessor->CancelLoads();
+    mXSLTProcessor = nullptr;
+  }
+
+  // release the nodes on stack
+  mContentStack.Clear();
+  mNotifyLevel = 0;
+
+  // return leaving the document empty if we're asked to not add a <parsererror>
+  // root node
+  if (mDocument->SuppressParserErrorElement()) {
+    return NS_OK;
+  }
+
+  // prepare to set <parsererror> as the document root
+  rv = HandleProcessingInstruction(
+      u"xml-stylesheet",
+      u"href=\"chrome://global/locale/intl.css\" type=\"text/css\"");
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  const char16_t* noAtts[] = {0, 0};
+
+  constexpr auto errorNs =
+      u"http://www.mozilla.org/newlayout/xml/parsererror.xml"_ns;
+
+  nsAutoString parsererror(errorNs);
+  parsererror.Append((char16_t)0xFFFF);
+  parsererror.AppendLiteral("parsererror");
+
+  rv = HandleStartElement(parsererror.get(), noAtts, 0, (uint32_t)-1, false);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = HandleCharacterData(aErrorText, NS_strlen(aErrorText), false);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsAutoString sourcetext(errorNs);
+  sourcetext.Append((char16_t)0xFFFF);
+  sourcetext.AppendLiteral("sourcetext");
+
+  rv = HandleStartElement(sourcetext.get(), noAtts, 0, (uint32_t)-1, false);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = HandleCharacterData(aSourceText, NS_strlen(aSourceText), false);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = HandleEndElement(sourcetext.get(), false);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = HandleEndElement(parsererror.get(), false);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  FlushTags();
+
+  return NS_OK;
+}
+
+nsresult nsXMLContentSink::AddAttributes(const char16_t** aAtts,
+                                         Element* aContent) {
+  // Add tag attributes to the content attributes
+  RefPtr<nsAtom> prefix, localName;
+  while (*aAtts) {
+    int32_t nameSpaceID;
+    nsContentUtils::SplitExpatName(aAtts[0], getter_AddRefs(prefix),
+                                   getter_AddRefs(localName), &nameSpaceID);
+
+    // Add attribute to content
+    aContent->SetAttr(nameSpaceID, localName, prefix,
+                      nsDependentString(aAtts[1]), false);
+    aAtts += 2;
+  }
+
+  return NS_OK;
+}
+
+#define NS_ACCUMULATION_BUFFER_SIZE 4096
+
+nsresult nsXMLContentSink::AddText(const char16_t* aText, int32_t aLength) {
+  // Copy data from string into our buffer; flush buffer when it fills up.
+  int32_t offset = 0;
+  while (0 != aLength) {
+    int32_t amount = NS_ACCUMULATION_BUFFER_SIZE - mTextLength;
+    if (0 == amount) {
+      nsresult rv = FlushText(false);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return rv;
+      }
+      MOZ_ASSERT(mTextLength == 0);
+      amount = NS_ACCUMULATION_BUFFER_SIZE;
+    }
+
+    if (amount > aLength) {
+      amount = aLength;
+    }
+    memcpy(&mText[mTextLength], &aText[offset], sizeof(char16_t) * amount);
+    mTextLength += amount;
+    offset += amount;
+    aLength -= amount;
+  }
+
+  return NS_OK;
+}
+
+void nsXMLContentSink::InitialTranslationCompleted() { StartLayout(false); }
+
+void nsXMLContentSink::FlushPendingNotifications(FlushType aType) {
+  // Only flush tags if we're not doing the notification ourselves
+  // (since we aren't reentrant)
+  if (!mInNotification) {
+    if (mIsDocumentObserver) {
+      // Only flush if we're still a document observer (so that our child
+      // counts should be correct).
+      if (aType >= FlushType::ContentAndNotify) {
+        FlushTags();
+      } else {
+        FlushText(false);
+      }
+    }
+    if (aType >= FlushType::EnsurePresShellInitAndFrames) {
+      // Make sure that layout has started so that the reflow flush
+      // will actually happen.
+      MaybeStartLayout(true);
+    }
+  }
+}
+
+/**
+ * NOTE!! Forked from SinkContext. Please keep in sync.
+ *
+ * Flush all elements that have been seen so far such that
+ * they are visible in the tree. Specifically, make sure
+ * that they are all added to their respective parents.
+ * Also, do notification at the top for all content that
+ * has been newly added so that the frame tree is complete.
+ */
+nsresult nsXMLContentSink::FlushTags() {
+  mDeferredFlushTags = false;
+  uint32_t oldUpdates = mUpdatesInNotification;
+
+  mUpdatesInNotification = 0;
+  ++mInNotification;
+  {
+    // Scope so we call EndUpdate before we decrease mInNotification
+    mozAutoDocUpdate updateBatch(mDocument, true);
+
+    // Don't release last text node in case we need to add to it again
+    FlushText(false);
+
+    // Start from the base of the stack (growing downward) and do
+    // a notification from the node that is closest to the root of
+    // tree for any content that has been added.
+
+    int32_t stackPos;
+    int32_t stackLen = mContentStack.Length();
+    bool flushed = false;
+    uint32_t childCount;
+    nsIContent* content;
+
+    for (stackPos = 0; stackPos < stackLen; ++stackPos) {
+      content = mContentStack[stackPos].mContent;
+      childCount = content->GetChildCount();
+
+      if (!flushed && (mContentStack[stackPos].mNumFlushed < childCount)) {
+        NotifyAppend(content, mContentStack[stackPos].mNumFlushed);
+        flushed = true;
+      }
+
+      mContentStack[stackPos].mNumFlushed = childCount;
+    }
+    mNotifyLevel = stackLen - 1;
+  }
+  --mInNotification;
+
+  if (mUpdatesInNotification > 1) {
+    UpdateChildCounts();
+  }
+
+  mUpdatesInNotification = oldUpdates;
+  return NS_OK;
+}
+
+/**
+ * NOTE!! Forked from SinkContext. Please keep in sync.
+ */
+void nsXMLContentSink::UpdateChildCounts() {
+  // Start from the top of the stack (growing upwards) and see if any
+  // new content has been appended. If so, we recognize that reflows
+  // have been generated for it and we should make sure that no
+  // further reflows occur.  Note that we have to include stackPos == 0
+  // to properly notify on kids of <html>.
+  int32_t stackLen = mContentStack.Length();
+  int32_t stackPos = stackLen - 1;
+  while (stackPos >= 0) {
+    StackNode& node = mContentStack[stackPos];
+    node.mNumFlushed = node.mContent->GetChildCount();
+
+    stackPos--;
+  }
+  mNotifyLevel = stackLen - 1;
+}
+
+bool nsXMLContentSink::IsMonolithicContainer(
+    mozilla::dom::NodeInfo* aNodeInfo) {
+  return ((aNodeInfo->NamespaceID() == kNameSpaceID_XHTML &&
+           (aNodeInfo->NameAtom() == nsGkAtoms::tr ||
+            aNodeInfo->NameAtom() == nsGkAtoms::select ||
+            aNodeInfo->NameAtom() == nsGkAtoms::object)) ||
+          (aNodeInfo->NamespaceID() == kNameSpaceID_MathML &&
+           (aNodeInfo->NameAtom() == nsGkAtoms::math)));
+}
+
+void nsXMLContentSink::ContinueInterruptedParsingIfEnabled() {
+  if (mParser && mParser->IsParserEnabled()) {
+    GetParser()->ContinueInterruptedParsing();
+  }
+}
+
+void nsXMLContentSink::ContinueInterruptedParsingAsync() {
+  nsCOMPtr<nsIRunnable> ev = NewRunnableMethod(
+      "nsXMLContentSink::ContinueInterruptedParsingIfEnabled", this,
+      &nsXMLContentSink::ContinueInterruptedParsingIfEnabled);
+
+  mDocument->Dispatch(mozilla::TaskCategory::Other, ev.forget());
+}
+
+nsIParser* nsXMLContentSink::GetParser() {
+  return static_cast<nsIParser*>(mParser.get());
+}