parser/html/nsHtml5StreamParser.cpp
author Csoregi Natalia <ncsoregi@mozilla.com>
Thu, 25 Oct 2018 01:26:25 +0300
changeset 442871 2ab590b3ed3f6534c07bae569ec3c84311b1e82b
parent 441873 fd914881db604175bdd129d62ec1cb3c8d0a0386
child 445888 577c34da7b73f1d33026ff0c768ace3e893c34b8
permissions -rw-r--r--
Backed out changeset 7b87be447ed8 (bug 1499821) for bustages on nsTransferable.h. CLOSED TREE

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set sw=2 ts=2 et tw=79: */
/* 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 "nsHtml5StreamParser.h"

#include "mozilla/DebugOnly.h"
#include "mozilla/Encoding.h"
#include "nsContentUtils.h"
#include "nsCyrillicDetector.h"
#include "nsHtml5Tokenizer.h"
#include "nsIHttpChannel.h"
#include "nsHtml5Parser.h"
#include "nsHtml5TreeBuilder.h"
#include "nsHtml5AtomTable.h"
#include "nsHtml5Module.h"
#include "nsHtml5StreamParserPtr.h"
#include "nsIDocShell.h"
#include "nsIScriptError.h"
#include "mozilla/Preferences.h"
#include "mozilla/StaticPrefs.h"
#include "mozilla/SystemGroup.h"
#include "mozilla/UniquePtrExtensions.h"
#include "nsHtml5Highlighter.h"
#include "expat_config.h"
#include "expat.h"
#include "nsINestedURI.h"
#include "nsCharsetSource.h"
#include "nsIWyciwygChannel.h"
#include "nsIThreadRetargetableRequest.h"
#include "nsPrintfCString.h"
#include "nsNetUtil.h"
#include "nsUdetXPCOMWrapper.h"
#include "nsXULAppAPI.h"
#include "mozilla/SchedulerGroup.h"
#include "nsJSEnvironment.h"

using namespace mozilla;

/*
 * Note that nsHtml5StreamParser implements cycle collecting AddRef and
 * Release. Therefore, nsHtml5StreamParser must never be refcounted from
 * the parser thread!
 *
 * To work around this limitation, runnables posted by the main thread to the
 * parser thread hold their reference to the stream parser in an
 * nsHtml5StreamParserPtr. Upon creation, nsHtml5StreamParserPtr addrefs the
 * object it holds
 * just like a regular nsRefPtr. This is OK, since the creation of the
 * runnable and the nsHtml5StreamParserPtr happens on the main thread.
 *
 * When the runnable is done on the parser thread, the destructor of
 * nsHtml5StreamParserPtr runs there. It doesn't call Release on the held object
 * directly. Instead, it posts another runnable back to the main thread where
 * that runnable calls Release on the wrapped object.
 *
 * When posting runnables in the other direction, the runnables have to be
 * created on the main thread when nsHtml5StreamParser is instantiated and
 * held for the lifetime of the nsHtml5StreamParser. This works, because the
 * same runnabled can be dispatched multiple times and currently runnables
 * posted from the parser thread to main thread don't need to wrap any
 * runnable-specific data. (In the other direction, the runnables most notably
 * wrap the byte data of the stream.)
 */
NS_IMPL_CYCLE_COLLECTING_ADDREF(nsHtml5StreamParser)
NS_IMPL_CYCLE_COLLECTING_RELEASE(nsHtml5StreamParser)

NS_INTERFACE_TABLE_HEAD(nsHtml5StreamParser)
  NS_INTERFACE_TABLE(nsHtml5StreamParser, nsICharsetDetectionObserver)
  NS_INTERFACE_TABLE_TO_MAP_SEGUE_CYCLE_COLLECTION(nsHtml5StreamParser)
NS_INTERFACE_MAP_END

NS_IMPL_CYCLE_COLLECTION_CLASS(nsHtml5StreamParser)

NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsHtml5StreamParser)
  tmp->DropTimer();
  NS_IMPL_CYCLE_COLLECTION_UNLINK(mObserver)
  NS_IMPL_CYCLE_COLLECTION_UNLINK(mRequest)
  NS_IMPL_CYCLE_COLLECTION_UNLINK(mOwner)
  tmp->mExecutorFlusher = nullptr;
  tmp->mLoadFlusher = nullptr;
  tmp->mExecutor = nullptr;
  NS_IMPL_CYCLE_COLLECTION_UNLINK(mChardet)
NS_IMPL_CYCLE_COLLECTION_UNLINK_END

NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(nsHtml5StreamParser)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mObserver)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mRequest)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mOwner)
  // hack: count the strongly owned edge wrapped in the runnable
  if (tmp->mExecutorFlusher) {
    NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mExecutorFlusher->mExecutor");
    cb.NoteXPCOMChild(static_cast<nsIContentSink*>(tmp->mExecutor));
  }
  // hack: count the strongly owned edge wrapped in the runnable
  if (tmp->mLoadFlusher) {
    NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mLoadFlusher->mExecutor");
    cb.NoteXPCOMChild(static_cast<nsIContentSink*>(tmp->mExecutor));
  }
  // hack: count self if held by mChardet
  if (tmp->mChardet) {
    NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mChardet->mObserver");
    cb.NoteXPCOMChild(static_cast<nsICharsetDetectionObserver*>(tmp));
  }
NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END

class nsHtml5ExecutorFlusher : public Runnable
{
private:
  RefPtr<nsHtml5TreeOpExecutor> mExecutor;

public:
  explicit nsHtml5ExecutorFlusher(nsHtml5TreeOpExecutor* aExecutor)
    : Runnable("nsHtml5ExecutorFlusher")
    , mExecutor(aExecutor)
  {
  }
  NS_IMETHOD Run() override
  {
    if (!mExecutor->isInList()) {
      mExecutor->RunFlushLoop();
    }
    return NS_OK;
  }
};

class nsHtml5LoadFlusher : public Runnable
{
private:
  RefPtr<nsHtml5TreeOpExecutor> mExecutor;

public:
  explicit nsHtml5LoadFlusher(nsHtml5TreeOpExecutor* aExecutor)
    : Runnable("nsHtml5LoadFlusher")
    , mExecutor(aExecutor)
  {
  }
  NS_IMETHOD Run() override
  {
    mExecutor->FlushSpeculativeLoads();
    return NS_OK;
  }
};

nsHtml5StreamParser::nsHtml5StreamParser(nsHtml5TreeOpExecutor* aExecutor,
                                         nsHtml5Parser* aOwner,
                                         eParserMode aMode)
  : mSniffingLength(0)
  , mBomState(eBomState::BOM_SNIFFING_NOT_STARTED)
  , mCharsetSource(kCharsetUninitialized)
  , mEncoding(WINDOWS_1252_ENCODING)
  , mReparseForbidden(false)
  , mLastBuffer(nullptr) // Will be filled when starting
  , mExecutor(aExecutor)
  , mTreeBuilder(new nsHtml5TreeBuilder(
      (aMode == VIEW_SOURCE_HTML || aMode == VIEW_SOURCE_XML)
        ? nullptr
        : mExecutor->GetStage(),
      aMode == NORMAL ? mExecutor->GetStage() : nullptr))
  , mTokenizer(new nsHtml5Tokenizer(mTreeBuilder, aMode == VIEW_SOURCE_XML))
  , mTokenizerMutex("nsHtml5StreamParser mTokenizerMutex")
  , mOwner(aOwner)
  , mLastWasCR(false)
  , mStreamState(eHtml5StreamState::STREAM_NOT_STARTED)
  , mSpeculating(false)
  , mAtEOF(false)
  , mSpeculationMutex("nsHtml5StreamParser mSpeculationMutex")
  , mSpeculationFailureCount(0)
  , mTerminated(false)
  , mInterrupted(false)
  , mTerminatedMutex("nsHtml5StreamParser mTerminatedMutex")
  , mEventTarget(nsHtml5Module::GetStreamParserThread()->SerialEventTarget())
  , mExecutorFlusher(new nsHtml5ExecutorFlusher(aExecutor))
  , mLoadFlusher(new nsHtml5LoadFlusher(aExecutor))
  , mFeedChardet(false)
  , mInitialEncodingWasFromParentFrame(false)
  , mHasHadErrors(false)
  , mFlushTimer(NS_NewTimer(mEventTarget))
  , mFlushTimerMutex("nsHtml5StreamParser mFlushTimerMutex")
  , mFlushTimerArmed(false)
  , mFlushTimerEverFired(false)
  , mMode(aMode)
{
  NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
#ifdef DEBUG
  mAtomTable.SetPermittedLookupEventTarget(mEventTarget);
#endif
  mTokenizer->setInterner(&mAtomTable);
  mTokenizer->setEncodingDeclarationHandler(this);

  if (aMode == VIEW_SOURCE_HTML || aMode == VIEW_SOURCE_XML) {
    nsHtml5Highlighter* highlighter =
      new nsHtml5Highlighter(mExecutor->GetStage());
    mTokenizer->EnableViewSource(highlighter);   // takes ownership
    mTreeBuilder->EnableViewSource(highlighter); // doesn't own
  }

  // Chardet instantiation adapted from File.
  // Chardet is initialized here even if it turns out to be useless
  // to make the chardet refcount its observer (nsHtml5StreamParser)
  // on the main thread.
  nsAutoCString detectorName;
  Preferences::GetLocalizedCString("intl.charset.detector", detectorName);
  if (!detectorName.IsEmpty()) {
    // We recognize one of the three magic strings for the following languages.
    if (detectorName.EqualsLiteral("ruprob")) {
      mChardet = new nsRUProbDetector();
    } else if (detectorName.EqualsLiteral("ukprob")) {
      mChardet = new nsUKProbDetector();
    } else if (detectorName.EqualsLiteral("ja_parallel_state_machine")) {
      mChardet = new nsJAPSMDetector();
    } else {
      mChardet = nullptr;
    }
    if (mChardet) {
      (void)mChardet->Init(this);
      mFeedChardet = true;
    }
  }

  // There's a zeroing operator new for everything else
}

nsHtml5StreamParser::~nsHtml5StreamParser()
{
  NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
  mTokenizer->end();
  if (recordreplay::IsRecordingOrReplaying()) {
    recordreplay::EndContentParse(this);
  }
#ifdef DEBUG
  {
    mozilla::MutexAutoLock flushTimerLock(mFlushTimerMutex);
    MOZ_ASSERT(!mFlushTimer, "Flush timer was not dropped before dtor!");
  }
  mRequest = nullptr;
  mObserver = nullptr;
  mUnicodeDecoder = nullptr;
  mSniffingBuffer = nullptr;
  mMetaScanner = nullptr;
  mFirstBuffer = nullptr;
  mExecutor = nullptr;
  mTreeBuilder = nullptr;
  mTokenizer = nullptr;
  mOwner = nullptr;
#endif
}

nsresult
nsHtml5StreamParser::GetChannel(nsIChannel** aChannel)
{
  NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
  return mRequest ? CallQueryInterface(mRequest, aChannel)
                  : NS_ERROR_NOT_AVAILABLE;
}

NS_IMETHODIMP
nsHtml5StreamParser::Notify(const char* aCharset, nsDetectionConfident aConf)
{
  NS_ASSERTION(IsParserThread(), "Wrong thread!");
  if (aConf == eBestAnswer || aConf == eSureAnswer) {
    mFeedChardet = false; // just in case
    auto encoding =
      Encoding::ForLabelNoReplacement(nsDependentCString(aCharset));
    if (!encoding) {
      return NS_OK;
    }
    if (HasDecoder()) {
      if (mEncoding == encoding) {
        NS_ASSERTION(mCharsetSource < kCharsetFromAutoDetection,
                     "Why are we running chardet at all?");
        mCharsetSource = kCharsetFromAutoDetection;
        mTreeBuilder->SetDocumentCharset(mEncoding, mCharsetSource);
      } else {
        // We've already committed to a decoder. Request a reload from the
        // docshell.
        mTreeBuilder->NeedsCharsetSwitchTo(
          WrapNotNull(encoding), kCharsetFromAutoDetection, 0);
        FlushTreeOpsAndDisarmTimer();
        Interrupt();
      }
    } else {
      // Got a confident answer from the sniffing buffer. That code will
      // take care of setting up the decoder.
      mEncoding = WrapNotNull(encoding);
      mCharsetSource = kCharsetFromAutoDetection;
      mTreeBuilder->SetDocumentCharset(mEncoding, mCharsetSource);
    }
  }
  return NS_OK;
}

void
nsHtml5StreamParser::SetViewSourceTitle(nsIURI* aURL)
{
  if (recordreplay::IsRecordingOrReplaying()) {
    nsAutoCString spec;
    aURL->GetSpec(spec);
    recordreplay::BeginContentParse(this, spec.get(), "text/html");
  }

  if (aURL) {
    nsCOMPtr<nsIURI> temp;
    bool isViewSource;
    aURL->SchemeIs("view-source", &isViewSource);
    if (isViewSource) {
      nsCOMPtr<nsINestedURI> nested = do_QueryInterface(aURL);
      nested->GetInnerURI(getter_AddRefs(temp));
    } else {
      temp = aURL;
    }
    bool isData;
    temp->SchemeIs("data", &isData);
    if (isData) {
      // Avoid showing potentially huge data: URLs. The three last bytes are
      // UTF-8 for an ellipsis.
      mViewSourceTitle.AssignLiteral("data:\xE2\x80\xA6");
    } else {
      nsresult rv = temp->GetSpec(mViewSourceTitle);
      if (NS_FAILED(rv)) {
        mViewSourceTitle.AssignLiteral("\xE2\x80\xA6");
      }
    }
  }
}

nsresult
nsHtml5StreamParser::SetupDecodingAndWriteSniffingBufferAndCurrentSegment(
  const uint8_t* aFromSegment, // can be null
  uint32_t aCount,
  uint32_t* aWriteCount)
{
  NS_ASSERTION(IsParserThread(), "Wrong thread!");
  nsresult rv = NS_OK;
  mUnicodeDecoder = mEncoding->NewDecoderWithBOMRemoval();
  if (mSniffingBuffer) {
    uint32_t writeCount;
    rv = WriteStreamBytes(mSniffingBuffer.get(), mSniffingLength, &writeCount);
    NS_ENSURE_SUCCESS(rv, rv);
    mSniffingBuffer = nullptr;
  }
  mMetaScanner = nullptr;
  if (aFromSegment) {
    rv = WriteStreamBytes(aFromSegment, aCount, aWriteCount);
  }
  return rv;
}

nsresult
nsHtml5StreamParser::SetupDecodingFromBom(NotNull<const Encoding*> aEncoding)
{
  NS_ASSERTION(IsParserThread(), "Wrong thread!");
  mEncoding = aEncoding;
  mUnicodeDecoder = mEncoding->NewDecoderWithoutBOMHandling();
  mCharsetSource = kCharsetFromByteOrderMark;
  mFeedChardet = false;
  mTreeBuilder->SetDocumentCharset(mEncoding, mCharsetSource);
  mSniffingBuffer = nullptr;
  mMetaScanner = nullptr;
  mBomState = BOM_SNIFFING_OVER;
  return NS_OK;
}

void
nsHtml5StreamParser::SniffBOMlessUTF16BasicLatin(const uint8_t* aFromSegment,
                                                 uint32_t aCountToSniffingLimit)
{
  // Avoid underspecified heuristic craziness for XHR
  if (mMode == LOAD_AS_DATA) {
    return;
  }
  // Make sure there's enough data. Require room for "<title></title>"
  if (mSniffingLength + aCountToSniffingLimit < 30) {
    return;
  }
  // even-numbered bytes tracked at 0, odd-numbered bytes tracked at 1
  bool byteZero[2] = { false, false };
  bool byteNonZero[2] = { false, false };
  uint32_t i = 0;
  if (mSniffingBuffer) {
    for (; i < mSniffingLength; ++i) {
      if (mSniffingBuffer[i]) {
        if (byteNonZero[1 - (i % 2)]) {
          return;
        }
        byteNonZero[i % 2] = true;
      } else {
        if (byteZero[1 - (i % 2)]) {
          return;
        }
        byteZero[i % 2] = true;
      }
    }
  }
  if (aFromSegment) {
    for (uint32_t j = 0; j < aCountToSniffingLimit; ++j) {
      if (aFromSegment[j]) {
        if (byteNonZero[1 - ((i + j) % 2)]) {
          return;
        }
        byteNonZero[(i + j) % 2] = true;
      } else {
        if (byteZero[1 - ((i + j) % 2)]) {
          return;
        }
        byteZero[(i + j) % 2] = true;
      }
    }
  }

  if (byteNonZero[0]) {
    mEncoding = UTF_16LE_ENCODING;
  } else {
    mEncoding = UTF_16BE_ENCODING;
  }
  mCharsetSource = kCharsetFromIrreversibleAutoDetection;
  mTreeBuilder->SetDocumentCharset(mEncoding, mCharsetSource);
  mFeedChardet = false;
  mTreeBuilder->MaybeComplainAboutCharset("EncBomlessUtf16", true, 0);
}

void
nsHtml5StreamParser::SetEncodingFromExpat(const char16_t* aEncoding)
{
  if (aEncoding) {
    nsDependentString utf16(aEncoding);
    nsAutoCString utf8;
    CopyUTF16toUTF8(utf16, utf8);
    auto encoding = PreferredForInternalEncodingDecl(utf8);
    if (encoding) {
      mEncoding = WrapNotNull(encoding);
      mCharsetSource = kCharsetFromMetaTag; // closest for XML
      return;
    }
    // else the page declared an encoding Gecko doesn't support and we'd
    // end up defaulting to UTF-8 anyway. Might as well fall through here
    // right away and let the encoding be set to UTF-8 which we'd default to
    // anyway.
  }
  mEncoding = UTF_8_ENCODING;           // XML defaults to UTF-8 without a BOM
  mCharsetSource = kCharsetFromMetaTag; // means confident
}

// A separate user data struct is used instead of passing the
// nsHtml5StreamParser instance as user data in order to avoid including
// expat.h in nsHtml5StreamParser.h. Doing that would cause naming conflicts.
// Using a separate user data struct also avoids bloating nsHtml5StreamParser
// by one pointer.
struct UserData
{
  XML_Parser mExpat;
  nsHtml5StreamParser* mStreamParser;
};

// Using no-namespace handler callbacks to avoid including expat.h in
// nsHtml5StreamParser.h, since doing so would cause naming conclicts.
static void
HandleXMLDeclaration(void* aUserData,
                     const XML_Char* aVersion,
                     const XML_Char* aEncoding,
                     int aStandalone)
{
  UserData* ud = static_cast<UserData*>(aUserData);
  ud->mStreamParser->SetEncodingFromExpat(
    reinterpret_cast<const char16_t*>(aEncoding));
  XML_StopParser(ud->mExpat, false);
}

static void
HandleStartElement(void* aUserData,
                   const XML_Char* aName,
                   const XML_Char** aAtts)
{
  UserData* ud = static_cast<UserData*>(aUserData);
  XML_StopParser(ud->mExpat, false);
}

static void
HandleEndElement(void* aUserData, const XML_Char* aName)
{
  UserData* ud = static_cast<UserData*>(aUserData);
  XML_StopParser(ud->mExpat, false);
}

static void
HandleComment(void* aUserData, const XML_Char* aName)
{
  UserData* ud = static_cast<UserData*>(aUserData);
  XML_StopParser(ud->mExpat, false);
}

static void
HandleProcessingInstruction(void* aUserData,
                            const XML_Char* aTarget,
                            const XML_Char* aData)
{
  UserData* ud = static_cast<UserData*>(aUserData);
  XML_StopParser(ud->mExpat, false);
}

nsresult
nsHtml5StreamParser::FinalizeSniffing(
  const uint8_t* aFromSegment, // can be null
  uint32_t aCount,
  uint32_t* aWriteCount,
  uint32_t aCountToSniffingLimit)
{
  NS_ASSERTION(IsParserThread(), "Wrong thread!");
  NS_ASSERTION(mCharsetSource < kCharsetFromParentForced,
               "Should not finalize sniffing when using forced charset.");
  if (mMode == VIEW_SOURCE_XML) {
    static const XML_Memory_Handling_Suite memsuite = {
      (void* (*)(size_t))moz_xmalloc,
      (void* (*)(void*, size_t))moz_xrealloc,
      free
    };

    static const char16_t kExpatSeparator[] = { 0xFFFF, '\0' };

    static const char16_t kISO88591[] = { 'I', 'S', 'O', '-', '8', '8',
                                          '5', '9', '-', '1', '\0' };

    UserData ud;
    ud.mStreamParser = this;

    // If we got this far, the stream didn't have a BOM. UTF-16-encoded XML
    // documents MUST begin with a BOM. We don't support EBCDIC and such.
    // Thus, at this point, what we have is garbage or something encoded using
    // a rough ASCII superset. ISO-8859-1 allows us to decode ASCII bytes
    // without throwing errors when bytes have the most significant bit set
    // and without triggering expat's unknown encoding code paths. This is
    // enough to be able to use expat to parse the XML declaration in order
    // to extract the encoding name from it.
    ud.mExpat = XML_ParserCreate_MM(kISO88591, &memsuite, kExpatSeparator);
    XML_SetXmlDeclHandler(ud.mExpat, HandleXMLDeclaration);
    XML_SetElementHandler(ud.mExpat, HandleStartElement, HandleEndElement);
    XML_SetCommentHandler(ud.mExpat, HandleComment);
    XML_SetProcessingInstructionHandler(ud.mExpat, HandleProcessingInstruction);
    XML_SetUserData(ud.mExpat, static_cast<void*>(&ud));

    XML_Status status = XML_STATUS_OK;

    // aFromSegment points to the data obtained from the current network
    // event. mSniffingBuffer (if it exists) contains the data obtained before
    // the current event. Thus, mSniffingLenth bytes of mSniffingBuffer
    // followed by aCountToSniffingLimit bytes from aFromSegment are the
    // first 1024 bytes of the file (or the file as a whole if the file is
    // 1024 bytes long or shorter). Thus, we parse both buffers, but if the
    // first call succeeds already, we skip parsing the second buffer.
    if (mSniffingBuffer) {
      status = XML_Parse(ud.mExpat,
                         reinterpret_cast<const char*>(mSniffingBuffer.get()),
                         mSniffingLength,
                         false);
    }
    if (status == XML_STATUS_OK && mCharsetSource < kCharsetFromMetaTag &&
        aFromSegment) {
      status = XML_Parse(ud.mExpat,
                         reinterpret_cast<const char*>(aFromSegment),
                         aCountToSniffingLimit,
                         false);
    }
    XML_ParserFree(ud.mExpat);

    if (mCharsetSource < kCharsetFromMetaTag) {
      // Failed to get an encoding from the XML declaration. XML defaults
      // confidently to UTF-8 in this case.
      // It is also possible that the document has an XML declaration that is
      // longer than 1024 bytes, but that case is not worth worrying about.
      mEncoding = UTF_8_ENCODING;
      mCharsetSource = kCharsetFromMetaTag; // means confident
    }

    return SetupDecodingAndWriteSniffingBufferAndCurrentSegment(
      aFromSegment, aCount, aWriteCount);
  }

  // meta scan failed.
  if (mCharsetSource >= kCharsetFromHintPrevDoc) {
    mFeedChardet = false;
    return SetupDecodingAndWriteSniffingBufferAndCurrentSegment(
      aFromSegment, aCount, aWriteCount);
  }
  // Check for BOMless UTF-16 with Basic
  // Latin content for compat with IE. See bug 631751.
  SniffBOMlessUTF16BasicLatin(aFromSegment, aCountToSniffingLimit);
  // the charset may have been set now
  // maybe try chardet now;
  if (mFeedChardet) {
    bool dontFeed;
    nsresult rv;
    if (mSniffingBuffer) {
      rv = mChardet->DoIt(
        (const char*)mSniffingBuffer.get(), mSniffingLength, &dontFeed);
      mFeedChardet = !dontFeed;
      NS_ENSURE_SUCCESS(rv, rv);
    }
    if (mFeedChardet && aFromSegment) {
      rv = mChardet->DoIt((const char*)aFromSegment,
                          // Avoid buffer boundary-dependent behavior when
                          // reparsing is forbidden. If reparse is forbidden,
                          // act as if we only saw the first 1024 bytes.
                          // When reparsing isn't forbidden, buffer boundaries
                          // can have an effect on whether the page is loaded
                          // once or twice. :-(
                          mReparseForbidden ? aCountToSniffingLimit : aCount,
                          &dontFeed);
      mFeedChardet = !dontFeed;
      NS_ENSURE_SUCCESS(rv, rv);
    }
    if (mFeedChardet && (!aFromSegment || mReparseForbidden)) {
      // mReparseForbidden is checked so that we get to use the sniffing
      // buffer with the best guess so far if we aren't allowed to guess
      // better later.
      mFeedChardet = false;
      rv = mChardet->Done();
      NS_ENSURE_SUCCESS(rv, rv);
    }
    // fall thru; callback may have changed charset
  }
  if (mCharsetSource == kCharsetUninitialized) {
    // Hopefully this case is never needed, but dealing with it anyway
    mEncoding = WINDOWS_1252_ENCODING;
    mCharsetSource = kCharsetFromFallback;
    mTreeBuilder->SetDocumentCharset(mEncoding, mCharsetSource);
  } else if (mMode == LOAD_AS_DATA && mCharsetSource == kCharsetFromFallback) {
    NS_ASSERTION(mReparseForbidden, "Reparse should be forbidden for XHR");
    NS_ASSERTION(!mFeedChardet, "Should not feed chardet for XHR");
    NS_ASSERTION(mEncoding == UTF_8_ENCODING, "XHR should default to UTF-8");
    // Now mark charset source as non-weak to signal that we have a decision
    mCharsetSource = kCharsetFromDocTypeDefault;
    mTreeBuilder->SetDocumentCharset(mEncoding, mCharsetSource);
  }
  return SetupDecodingAndWriteSniffingBufferAndCurrentSegment(
    aFromSegment, aCount, aWriteCount);
}

nsresult
nsHtml5StreamParser::SniffStreamBytes(const uint8_t* aFromSegment,
                                      uint32_t aCount,
                                      uint32_t* aWriteCount)
{
  NS_ASSERTION(IsParserThread(), "Wrong thread!");
  nsresult rv = NS_OK;
  uint32_t writeCount;

  // mEncoding and mCharsetSource potentially have come from channel or higher
  // by now. If we find a BOM, SetupDecodingFromBom() will overwrite them.
  // If we don't find a BOM, the previously set values of mEncoding and
  // mCharsetSource are not modified by the BOM sniffing here.
  for (uint32_t i = 0; i < aCount && mBomState != BOM_SNIFFING_OVER; i++) {
    switch (mBomState) {
      case BOM_SNIFFING_NOT_STARTED:
        NS_ASSERTION(i == 0, "Bad BOM sniffing state.");
        switch (*aFromSegment) {
          case 0xEF:
            mBomState = SEEN_UTF_8_FIRST_BYTE;
            break;
          case 0xFF:
            mBomState = SEEN_UTF_16_LE_FIRST_BYTE;
            break;
          case 0xFE:
            mBomState = SEEN_UTF_16_BE_FIRST_BYTE;
            break;
          default:
            mBomState = BOM_SNIFFING_OVER;
            break;
        }
        break;
      case SEEN_UTF_16_LE_FIRST_BYTE:
        if (aFromSegment[i] == 0xFE) {
          rv = SetupDecodingFromBom(
            UTF_16LE_ENCODING); // upper case is the raw form
          NS_ENSURE_SUCCESS(rv, rv);
          uint32_t count = aCount - (i + 1);
          rv = WriteStreamBytes(aFromSegment + (i + 1), count, &writeCount);
          NS_ENSURE_SUCCESS(rv, rv);
          *aWriteCount = writeCount + (i + 1);
          return rv;
        }
        mBomState = BOM_SNIFFING_OVER;
        break;
      case SEEN_UTF_16_BE_FIRST_BYTE:
        if (aFromSegment[i] == 0xFF) {
          rv = SetupDecodingFromBom(
            UTF_16BE_ENCODING); // upper case is the raw form
          NS_ENSURE_SUCCESS(rv, rv);
          uint32_t count = aCount - (i + 1);
          rv = WriteStreamBytes(aFromSegment + (i + 1), count, &writeCount);
          NS_ENSURE_SUCCESS(rv, rv);
          *aWriteCount = writeCount + (i + 1);
          return rv;
        }
        mBomState = BOM_SNIFFING_OVER;
        break;
      case SEEN_UTF_8_FIRST_BYTE:
        if (aFromSegment[i] == 0xBB) {
          mBomState = SEEN_UTF_8_SECOND_BYTE;
        } else {
          mBomState = BOM_SNIFFING_OVER;
        }
        break;
      case SEEN_UTF_8_SECOND_BYTE:
        if (aFromSegment[i] == 0xBF) {
          rv =
            SetupDecodingFromBom(UTF_8_ENCODING); // upper case is the raw form
          NS_ENSURE_SUCCESS(rv, rv);
          uint32_t count = aCount - (i + 1);
          rv = WriteStreamBytes(aFromSegment + (i + 1), count, &writeCount);
          NS_ENSURE_SUCCESS(rv, rv);
          *aWriteCount = writeCount + (i + 1);
          return rv;
        }
        mBomState = BOM_SNIFFING_OVER;
        break;
      default:
        mBomState = BOM_SNIFFING_OVER;
        break;
    }
  }
  // if we get here, there either was no BOM or the BOM sniffing isn't complete
  // yet

  MOZ_ASSERT(mCharsetSource != kCharsetFromByteOrderMark,
             "Should not come here if BOM was found.");
  MOZ_ASSERT(mCharsetSource != kCharsetFromOtherComponent,
             "kCharsetFromOtherComponent is for XSLT.");

  if (mBomState == BOM_SNIFFING_OVER && mCharsetSource == kCharsetFromChannel) {
    // There was no BOM and the charset came from channel. mEncoding
    // still contains the charset from the channel as set by an
    // earlier call to SetDocumentCharset(), since we didn't find a BOM and
    // overwrite mEncoding. (Note that if the user has overridden the charset,
    // we don't come here but check <meta> for XSS-dangerous charsets first.)
    mFeedChardet = false;
    mTreeBuilder->SetDocumentCharset(mEncoding, mCharsetSource);
    return SetupDecodingAndWriteSniffingBufferAndCurrentSegment(
      aFromSegment, aCount, aWriteCount);
  }

  if (!mMetaScanner &&
      (mMode == NORMAL || mMode == VIEW_SOURCE_HTML || mMode == LOAD_AS_DATA)) {
    mMetaScanner = new nsHtml5MetaScanner(mTreeBuilder);
  }

  if (mSniffingLength + aCount >= NS_HTML5_STREAM_PARSER_SNIFFING_BUFFER_SIZE) {
    // this is the last buffer
    uint32_t countToSniffingLimit =
      NS_HTML5_STREAM_PARSER_SNIFFING_BUFFER_SIZE - mSniffingLength;
    if (mMode == NORMAL || mMode == VIEW_SOURCE_HTML || mMode == LOAD_AS_DATA) {
      nsHtml5ByteReadable readable(aFromSegment,
                                   aFromSegment + countToSniffingLimit);
      nsAutoCString charset;
      auto encoding = mMetaScanner->sniff(&readable);
      // Due to the way nsHtml5Portability reports OOM, ask the tree buider
      nsresult rv;
      if (NS_FAILED((rv = mTreeBuilder->IsBroken()))) {
        MarkAsBroken(rv);
        return rv;
      }
      if (encoding) {
        // meta scan successful; honor overrides unless meta is XSS-dangerous
        if ((mCharsetSource == kCharsetFromParentForced ||
             mCharsetSource == kCharsetFromUserForced) &&
            (encoding->IsAsciiCompatible() ||
             encoding == ISO_2022_JP_ENCODING)) {
          // Honor override
          return SetupDecodingAndWriteSniffingBufferAndCurrentSegment(
            aFromSegment, aCount, aWriteCount);
        }
        mEncoding = WrapNotNull(encoding);
        mCharsetSource = kCharsetFromMetaPrescan;
        mFeedChardet = false;
        mTreeBuilder->SetDocumentCharset(mEncoding, mCharsetSource);
        return SetupDecodingAndWriteSniffingBufferAndCurrentSegment(
          aFromSegment, aCount, aWriteCount);
      }
    }
    if (mCharsetSource == kCharsetFromParentForced ||
        mCharsetSource == kCharsetFromUserForced) {
      // meta not found, honor override
      return SetupDecodingAndWriteSniffingBufferAndCurrentSegment(
        aFromSegment, aCount, aWriteCount);
    }
    return FinalizeSniffing(
      aFromSegment, aCount, aWriteCount, countToSniffingLimit);
  }

  // not the last buffer
  if (mMode == NORMAL || mMode == VIEW_SOURCE_HTML || mMode == LOAD_AS_DATA) {
    nsHtml5ByteReadable readable(aFromSegment, aFromSegment + aCount);
    auto encoding = mMetaScanner->sniff(&readable);
    // Due to the way nsHtml5Portability reports OOM, ask the tree buider
    nsresult rv;
    if (NS_FAILED((rv = mTreeBuilder->IsBroken()))) {
      MarkAsBroken(rv);
      return rv;
    }
    if (encoding) {
      // meta scan successful; honor overrides unless meta is XSS-dangerous
      if ((mCharsetSource == kCharsetFromParentForced ||
           mCharsetSource == kCharsetFromUserForced) &&
          (encoding->IsAsciiCompatible() || encoding == ISO_2022_JP_ENCODING)) {
        // Honor override
        return SetupDecodingAndWriteSniffingBufferAndCurrentSegment(
          aFromSegment, aCount, aWriteCount);
      }
      mEncoding = WrapNotNull(encoding);
      mCharsetSource = kCharsetFromMetaPrescan;
      mFeedChardet = false;
      mTreeBuilder->SetDocumentCharset(mEncoding, mCharsetSource);
      return SetupDecodingAndWriteSniffingBufferAndCurrentSegment(
        aFromSegment, aCount, aWriteCount);
    }
  }

  if (!mSniffingBuffer) {
    mSniffingBuffer = MakeUniqueFallible<uint8_t[]>(
      NS_HTML5_STREAM_PARSER_SNIFFING_BUFFER_SIZE);
    if (!mSniffingBuffer) {
      return NS_ERROR_OUT_OF_MEMORY;
    }
  }
  memcpy(&mSniffingBuffer[mSniffingLength], aFromSegment, aCount);
  mSniffingLength += aCount;
  *aWriteCount = aCount;
  return NS_OK;
}

nsresult
nsHtml5StreamParser::WriteStreamBytes(const uint8_t* aFromSegment,
                                      uint32_t aCount,
                                      uint32_t* aWriteCount)
{
  NS_ASSERTION(IsParserThread(), "Wrong thread!");
  // mLastBuffer should always point to a buffer of the size
  // NS_HTML5_STREAM_PARSER_READ_BUFFER_SIZE.
  if (!mLastBuffer) {
    NS_WARNING("mLastBuffer should not be null!");
    MarkAsBroken(NS_ERROR_NULL_POINTER);
    return NS_ERROR_NULL_POINTER;
  }
  size_t totalRead = 0;
  auto src = MakeSpan(aFromSegment, aCount);
  for (;;) {
    auto dst = mLastBuffer->TailAsSpan(NS_HTML5_STREAM_PARSER_READ_BUFFER_SIZE);
    uint32_t result;
    size_t read;
    size_t written;
    bool hadErrors;
    Tie(result, read, written, hadErrors) =
      mUnicodeDecoder->DecodeToUTF16(src, dst, false);
    if (recordreplay::IsRecordingOrReplaying()) {
      recordreplay::AddContentParseData16(this, dst.data(), written);
    }
    if (hadErrors && !mHasHadErrors) {
      mHasHadErrors = true;
      if (mEncoding == UTF_8_ENCODING) {
        mTreeBuilder->TryToEnableEncodingMenu();
      }
    }
    src = src.From(read);
    totalRead += read;
    mLastBuffer->AdvanceEnd(written);
    if (result == kOutputFull) {
      RefPtr<nsHtml5OwningUTF16Buffer> newBuf =
        nsHtml5OwningUTF16Buffer::FalliblyCreate(
          NS_HTML5_STREAM_PARSER_READ_BUFFER_SIZE);
      if (!newBuf) {
        MarkAsBroken(NS_ERROR_OUT_OF_MEMORY);
        return NS_ERROR_OUT_OF_MEMORY;
      }
      mLastBuffer = (mLastBuffer->next = newBuf.forget());
    } else {
      MOZ_ASSERT(totalRead == aCount,
                 "The Unicode decoder consumed the wrong number of bytes.");
      *aWriteCount = totalRead;
      return NS_OK;
    }
  }
}

class MaybeRunCollector : public Runnable
{
public:
  explicit MaybeRunCollector(nsIDocShell* aDocShell)
    : Runnable("MaybeRunCollector")
    , mDocShell(aDocShell)
  {
  }

  NS_IMETHOD Run() override
  {
    nsJSContext::MaybeRunNextCollectorSlice(mDocShell,
                                            JS::gcreason::HTML_PARSER);
    return NS_OK;
  }

  nsCOMPtr<nsIDocShell> mDocShell;
};

nsresult
nsHtml5StreamParser::OnStartRequest(nsIRequest* aRequest, nsISupports* aContext)
{
  MOZ_RELEASE_ASSERT(STREAM_NOT_STARTED == mStreamState,
                     "Got OnStartRequest when the stream had already started.");
  MOZ_ASSERT(
    !mExecutor->HasStarted(),
    "Got OnStartRequest at the wrong stage in the executor life cycle.");
  NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
  if (mObserver) {
    mObserver->OnStartRequest(aRequest, aContext);
  }
  mRequest = aRequest;

  mStreamState = STREAM_BEING_READ;

  if (mMode == VIEW_SOURCE_HTML || mMode == VIEW_SOURCE_XML) {
    mTokenizer->StartViewSource(NS_ConvertUTF8toUTF16(mViewSourceTitle));
  }

  // For View Source, the parser should run with scripts "enabled" if a normal
  // load would have scripts enabled.
  bool scriptingEnabled =
    mMode == LOAD_AS_DATA ? false : mExecutor->IsScriptEnabled();
  mOwner->StartTokenizer(scriptingEnabled);

  bool isSrcdoc = false;
  nsCOMPtr<nsIChannel> channel;
  nsresult rv = GetChannel(getter_AddRefs(channel));
  if (NS_SUCCEEDED(rv)) {
    isSrcdoc = NS_IsSrcdocChannel(channel);
  }
  mTreeBuilder->setIsSrcdocDocument(isSrcdoc);
  mTreeBuilder->setScriptingEnabled(scriptingEnabled);
  mTreeBuilder->SetPreventScriptExecution(
    !((mMode == NORMAL) && scriptingEnabled));
  mTokenizer->start();
  mExecutor->Start();
  mExecutor->StartReadingFromStage();

  if (mMode == PLAIN_TEXT) {
    mTreeBuilder->StartPlainText();
    mTokenizer->StartPlainText();
  } else if (mMode == VIEW_SOURCE_PLAIN) {
    nsAutoString viewSourceTitle;
    CopyUTF8toUTF16(mViewSourceTitle, viewSourceTitle);
    mTreeBuilder->EnsureBufferSpace(viewSourceTitle.Length());
    mTreeBuilder->StartPlainTextViewSource(viewSourceTitle);
    mTokenizer->StartPlainText();
  }

  /*
   * If you move the following line, be very careful not to cause
   * WillBuildModel to be called before the document has had its
   * script global object set.
   */
  rv = mExecutor->WillBuildModel(eDTDMode_unknown);
  NS_ENSURE_SUCCESS(rv, rv);

  RefPtr<nsHtml5OwningUTF16Buffer> newBuf =
    nsHtml5OwningUTF16Buffer::FalliblyCreate(
      NS_HTML5_STREAM_PARSER_READ_BUFFER_SIZE);
  if (!newBuf) {
    // marks this stream parser as terminated,
    // which prevents entry to code paths that
    // would use mFirstBuffer or mLastBuffer.
    return mExecutor->MarkAsBroken(NS_ERROR_OUT_OF_MEMORY);
  }
  NS_ASSERTION(!mFirstBuffer, "How come we have the first buffer set?");
  NS_ASSERTION(!mLastBuffer, "How come we have the last buffer set?");
  mFirstBuffer = mLastBuffer = newBuf;

  rv = NS_OK;

  // The line below means that the encoding can end up being wrong if
  // a view-source URL is loaded without having the encoding hint from a
  // previous normal load in the history.
  mReparseForbidden = !(mMode == NORMAL || mMode == PLAIN_TEXT);

  mDocGroup = mExecutor->GetDocument()->GetDocGroup();

  nsCOMPtr<nsIHttpChannel> httpChannel(do_QueryInterface(mRequest, &rv));
  if (NS_SUCCEEDED(rv)) {
    // Non-HTTP channels are bogus enough that we let them work with unlabeled
    // runnables for now. Asserting for HTTP channels only.
    MOZ_ASSERT(mDocGroup || mMode == LOAD_AS_DATA,
               "How come the doc group is still null?");

    nsAutoCString method;
    Unused << httpChannel->GetRequestMethod(method);
    // XXX does Necko have a way to renavigate POST, etc. without hitting
    // the network?
    if (!method.EqualsLiteral("GET")) {
      // This is the old Gecko behavior but the HTML5 spec disagrees.
      // Don't reparse on POST.
      mReparseForbidden = true;
      mFeedChardet = false; // can't restart anyway
    }
  }

  // Attempt to retarget delivery of data (via OnDataAvailable) to the parser
  // thread, rather than through the main thread.
  nsCOMPtr<nsIThreadRetargetableRequest> threadRetargetableRequest =
    do_QueryInterface(mRequest, &rv);
  if (threadRetargetableRequest) {
    rv = threadRetargetableRequest->RetargetDeliveryTo(mEventTarget);
    if (NS_SUCCEEDED(rv)) {
      // Parser thread should be now ready to get data from necko and parse it
      // and main thread might have a chance to process a collector slice.
      // We need to do this asynchronously so that necko may continue processing
      // the request.
      nsCOMPtr<nsIRunnable> runnable =
        new MaybeRunCollector(mExecutor->GetDocument()->GetDocShell());
      mozilla::SystemGroup::Dispatch(mozilla::TaskCategory::GarbageCollection,
                                     runnable.forget());
    }
  }

  if (NS_FAILED(rv)) {
    NS_WARNING("Failed to retarget HTML data delivery to the parser thread.");
  }

  if (mCharsetSource == kCharsetFromParentFrame) {
    // Remember this in case chardet overwrites mCharsetSource
    mInitialEncodingWasFromParentFrame = true;
  }

  if (mCharsetSource >= kCharsetFromAutoDetection) {
    mFeedChardet = false;
  }

  nsCOMPtr<nsIWyciwygChannel> wyciwygChannel(do_QueryInterface(mRequest));
  if (mCharsetSource < kCharsetFromUtf8OnlyMime && !wyciwygChannel) {
    // we aren't ready to commit to an encoding yet
    // leave converter uninstantiated for now
    return NS_OK;
  }

  // We are reloading a document.open()ed doc or loading JSON/WebVTT/etc. into
  // a browsing context. In the latter case, there's no need to remove the
  // BOM manually here, because the UTF-8 decoder removes it.
  mReparseForbidden = true;
  mFeedChardet = false;

  // Instantiate the converter here to avoid BOM sniffing.
  mUnicodeDecoder = mEncoding->NewDecoderWithBOMRemoval();
  return NS_OK;
}

nsresult
nsHtml5StreamParser::CheckListenerChain()
{
  NS_ASSERTION(NS_IsMainThread(), "Should be on the main thread!");
  if (!mObserver) {
    return NS_OK;
  }
  nsresult rv;
  nsCOMPtr<nsIThreadRetargetableStreamListener> retargetable =
    do_QueryInterface(mObserver, &rv);
  if (NS_SUCCEEDED(rv) && retargetable) {
    rv = retargetable->CheckListenerChain();
  }
  return rv;
}

void
nsHtml5StreamParser::DoStopRequest()
{
  NS_ASSERTION(IsParserThread(), "Wrong thread!");
  MOZ_RELEASE_ASSERT(STREAM_BEING_READ == mStreamState,
                     "Stream ended without being open.");
  mTokenizerMutex.AssertCurrentThreadOwns();

  if (IsTerminated()) {
    return;
  }

  mStreamState = STREAM_ENDED;

  if (!mUnicodeDecoder) {
    uint32_t writeCount;
    nsresult rv;
    if (NS_FAILED(rv = FinalizeSniffing(nullptr, 0, &writeCount, 0))) {
      MarkAsBroken(rv);
      return;
    }
  } else if (mFeedChardet) {
    mChardet->Done();
  }

  MOZ_ASSERT(mUnicodeDecoder,
             "Should have a decoder after finalizing sniffing.");

  // mLastBuffer should always point to a buffer of the size
  // NS_HTML5_STREAM_PARSER_READ_BUFFER_SIZE.
  if (!mLastBuffer) {
    NS_WARNING("mLastBuffer should not be null!");
    MarkAsBroken(NS_ERROR_NULL_POINTER);
    return;
  }

  Span<uint8_t> src; // empty span
  for (;;) {
    auto dst = mLastBuffer->TailAsSpan(NS_HTML5_STREAM_PARSER_READ_BUFFER_SIZE);
    uint32_t result;
    size_t read;
    size_t written;
    bool hadErrors;
    Tie(result, read, written, hadErrors) =
      mUnicodeDecoder->DecodeToUTF16(src, dst, true);
    if (recordreplay::IsRecordingOrReplaying()) {
      recordreplay::AddContentParseData16(this, dst.data(), written);
    }
    if (hadErrors && !mHasHadErrors) {
      mHasHadErrors = true;
      if (mEncoding == UTF_8_ENCODING) {
        mTreeBuilder->TryToEnableEncodingMenu();
      }
    }
    MOZ_ASSERT(read == 0, "How come an empty span was read form?");
    mLastBuffer->AdvanceEnd(written);
    if (result == kOutputFull) {
      RefPtr<nsHtml5OwningUTF16Buffer> newBuf =
        nsHtml5OwningUTF16Buffer::FalliblyCreate(
          NS_HTML5_STREAM_PARSER_READ_BUFFER_SIZE);
      if (!newBuf) {
        MarkAsBroken(NS_ERROR_OUT_OF_MEMORY);
        return;
      }
      mLastBuffer = (mLastBuffer->next = newBuf.forget());
    } else {
      break;
    }
  }

  if (IsTerminatedOrInterrupted()) {
    return;
  }

  ParseAvailableData();
}

class nsHtml5RequestStopper : public Runnable
{
private:
  nsHtml5StreamParserPtr mStreamParser;

public:
  explicit nsHtml5RequestStopper(nsHtml5StreamParser* aStreamParser)
    : Runnable("nsHtml5RequestStopper")
    , mStreamParser(aStreamParser)
  {
  }
  NS_IMETHOD Run() override
  {
    mozilla::MutexAutoLock autoLock(mStreamParser->mTokenizerMutex);
    mStreamParser->DoStopRequest();
    return NS_OK;
  }
};

nsresult
nsHtml5StreamParser::OnStopRequest(nsIRequest* aRequest,
                                   nsISupports* aContext,
                                   nsresult status)
{
  NS_ASSERTION(mRequest == aRequest, "Got Stop on wrong stream.");
  NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
  if (mObserver) {
    mObserver->OnStopRequest(aRequest, aContext, status);
  }
  nsCOMPtr<nsIRunnable> stopper = new nsHtml5RequestStopper(this);
  if (NS_FAILED(mEventTarget->Dispatch(stopper, nsIThread::DISPATCH_NORMAL))) {
    NS_WARNING("Dispatching StopRequest event failed.");
  }
  return NS_OK;
}

void
nsHtml5StreamParser::DoDataAvailable(const uint8_t* aBuffer, uint32_t aLength)
{
  NS_ASSERTION(IsParserThread(), "Wrong thread!");
  MOZ_RELEASE_ASSERT(STREAM_BEING_READ == mStreamState,
                     "DoDataAvailable called when stream not open.");
  mTokenizerMutex.AssertCurrentThreadOwns();

  if (IsTerminated()) {
    return;
  }

  uint32_t writeCount;
  nsresult rv;
  if (HasDecoder()) {
    if (mFeedChardet) {
      bool dontFeed;
      mChardet->DoIt((const char*)aBuffer, aLength, &dontFeed);
      mFeedChardet = !dontFeed;
    }
    rv = WriteStreamBytes(aBuffer, aLength, &writeCount);
  } else {
    rv = SniffStreamBytes(aBuffer, aLength, &writeCount);
  }
  if (NS_FAILED(rv)) {
    MarkAsBroken(rv);
    return;
  }
  NS_ASSERTION(writeCount == aLength,
               "Wrong number of stream bytes written/sniffed.");

  if (IsTerminatedOrInterrupted()) {
    return;
  }

  ParseAvailableData();

  if (mFlushTimerArmed || mSpeculating) {
    return;
  }

  {
    mozilla::MutexAutoLock flushTimerLock(mFlushTimerMutex);
    mFlushTimer->InitWithNamedFuncCallback(
      nsHtml5StreamParser::TimerCallback,
      static_cast<void*>(this),
      mFlushTimerEverFired ? StaticPrefs::html5_flushtimer_initialdelay()
                           : StaticPrefs::html5_flushtimer_subsequentdelay(),
      nsITimer::TYPE_ONE_SHOT,
      "nsHtml5StreamParser::DoDataAvailable");
  }
  mFlushTimerArmed = true;
}

class nsHtml5DataAvailable : public Runnable
{
private:
  nsHtml5StreamParserPtr mStreamParser;
  UniquePtr<uint8_t[]> mData;
  uint32_t mLength;

public:
  nsHtml5DataAvailable(nsHtml5StreamParser* aStreamParser,
                       UniquePtr<uint8_t[]> aData,
                       uint32_t aLength)
    : Runnable("nsHtml5DataAvailable")
    , mStreamParser(aStreamParser)
    , mData(std::move(aData))
    , mLength(aLength)
  {
  }
  NS_IMETHOD Run() override
  {
    mozilla::MutexAutoLock autoLock(mStreamParser->mTokenizerMutex);
    mStreamParser->DoDataAvailable(mData.get(), mLength);
    return NS_OK;
  }
};

nsresult
nsHtml5StreamParser::OnDataAvailable(nsIRequest* aRequest,
                                     nsISupports* aContext,
                                     nsIInputStream* aInStream,
                                     uint64_t aSourceOffset,
                                     uint32_t aLength)
{
  nsresult rv;
  if (NS_FAILED(rv = mExecutor->IsBroken())) {
    return rv;
  }

  NS_ASSERTION(mRequest == aRequest, "Got data on wrong stream.");
  uint32_t totalRead;
  // Main thread to parser thread dispatch requires copying to buffer first.
  if (NS_IsMainThread()) {
    auto data = MakeUniqueFallible<uint8_t[]>(aLength);
    if (!data) {
      return mExecutor->MarkAsBroken(NS_ERROR_OUT_OF_MEMORY);
    }
    rv =
      aInStream->Read(reinterpret_cast<char*>(data.get()), aLength, &totalRead);
    NS_ENSURE_SUCCESS(rv, rv);
    NS_ASSERTION(totalRead <= aLength, "Read more bytes than were available?");

    nsCOMPtr<nsIRunnable> dataAvailable =
      new nsHtml5DataAvailable(this, std::move(data), totalRead);
    if (NS_FAILED(
          mEventTarget->Dispatch(dataAvailable, nsIThread::DISPATCH_NORMAL))) {
      NS_WARNING("Dispatching DataAvailable event failed.");
    }
    return rv;
  } else {
    NS_ASSERTION(IsParserThread(), "Wrong thread!");
    mozilla::MutexAutoLock autoLock(mTokenizerMutex);

    // Read directly from response buffer.
    rv =
      aInStream->ReadSegments(CopySegmentsToParser, this, aLength, &totalRead);
    if (NS_FAILED(rv)) {
      NS_WARNING("Failed reading response data to parser");
      return rv;
    }
    return NS_OK;
  }
}

/* static */ nsresult
nsHtml5StreamParser::CopySegmentsToParser(nsIInputStream* aInStream,
                                          void* aClosure,
                                          const char* aFromSegment,
                                          uint32_t aToOffset,
                                          uint32_t aCount,
                                          uint32_t* aWriteCount)
{
  nsHtml5StreamParser* parser = static_cast<nsHtml5StreamParser*>(aClosure);

  parser->DoDataAvailable((const uint8_t*)aFromSegment, aCount);
  // Assume DoDataAvailable consumed all available bytes.
  *aWriteCount = aCount;
  return NS_OK;
}

const Encoding*
nsHtml5StreamParser::PreferredForInternalEncodingDecl(
  const nsACString& aEncoding)
{
  const Encoding* newEncoding = Encoding::ForLabel(aEncoding);
  if (!newEncoding) {
    // the encoding name is bogus
    mTreeBuilder->MaybeComplainAboutCharset(
      "EncMetaUnsupported", true, mTokenizer->getLineNumber());
    return nullptr;
  }

  if (newEncoding == UTF_16BE_ENCODING || newEncoding == UTF_16LE_ENCODING) {
    mTreeBuilder->MaybeComplainAboutCharset(
      "EncMetaUtf16", true, mTokenizer->getLineNumber());
    newEncoding = UTF_8_ENCODING;
  }

  if (newEncoding == X_USER_DEFINED_ENCODING) {
    // WebKit/Blink hack for Indian and Armenian legacy sites
    mTreeBuilder->MaybeComplainAboutCharset(
      "EncMetaUserDefined", true, mTokenizer->getLineNumber());
    newEncoding = WINDOWS_1252_ENCODING;
  }

  if (newEncoding == mEncoding) {
    if (mCharsetSource < kCharsetFromMetaPrescan) {
      if (mInitialEncodingWasFromParentFrame) {
        mTreeBuilder->MaybeComplainAboutCharset(
          "EncLateMetaFrame", false, mTokenizer->getLineNumber());
      } else {
        mTreeBuilder->MaybeComplainAboutCharset(
          "EncLateMeta", false, mTokenizer->getLineNumber());
      }
    }
    mCharsetSource = kCharsetFromMetaTag; // become confident
    mFeedChardet = false;                 // don't feed chardet when confident
    return nullptr;
  }

  return newEncoding;
}

bool
nsHtml5StreamParser::internalEncodingDeclaration(nsHtml5String aEncoding)
{
  // This code needs to stay in sync with
  // nsHtml5MetaScanner::tryCharset. Unfortunately, the
  // trickery with member fields there leads to some copy-paste reuse. :-(
  NS_ASSERTION(IsParserThread(), "Wrong thread!");
  if (mCharsetSource >= kCharsetFromMetaTag) { // this threshold corresponds to
                                               // "confident" in the HTML5 spec
    return false;
  }

  nsString newEncoding16; // Not Auto, because using it to hold nsStringBuffer*
  aEncoding.ToString(newEncoding16);
  nsAutoCString newEncoding;
  CopyUTF16toUTF8(newEncoding16, newEncoding);

  auto encoding = PreferredForInternalEncodingDecl(newEncoding);
  if (!encoding) {
    return false;
  }

  if (mReparseForbidden) {
    // This mReparseForbidden check happens after the call to
    // PreferredForInternalEncodingDecl so that if that method calls
    // MaybeComplainAboutCharset, its charset complaint wins over the one
    // below.
    mTreeBuilder->MaybeComplainAboutCharset(
      "EncLateMetaTooLate", true, mTokenizer->getLineNumber());
    return false; // not reparsing even if we wanted to
  }

  // Avoid having the chardet ask for another restart after this restart
  // request.
  mFeedChardet = false;
  mTreeBuilder->NeedsCharsetSwitchTo(
    WrapNotNull(encoding), kCharsetFromMetaTag, mTokenizer->getLineNumber());
  FlushTreeOpsAndDisarmTimer();
  Interrupt();
  // the tree op executor will cause the stream parser to terminate
  // if the charset switch request is accepted or it'll uninterrupt
  // if the request failed. Note that if the restart request fails,
  // we don't bother trying to make chardet resume. Might as well
  // assume that chardet-requested restarts would fail, too.
  return true;
}

void
nsHtml5StreamParser::FlushTreeOpsAndDisarmTimer()
{
  NS_ASSERTION(IsParserThread(), "Wrong thread!");
  if (mFlushTimerArmed) {
    // avoid calling Cancel if the flush timer isn't armed to avoid acquiring
    // a mutex
    {
      mozilla::MutexAutoLock flushTimerLock(mFlushTimerMutex);
      mFlushTimer->Cancel();
    }
    mFlushTimerArmed = false;
  }
  if (mMode == VIEW_SOURCE_HTML || mMode == VIEW_SOURCE_XML) {
    mTokenizer->FlushViewSource();
  }
  mTreeBuilder->Flush();
  nsCOMPtr<nsIRunnable> runnable(mExecutorFlusher);
  if (NS_FAILED(DispatchToMain(runnable.forget()))) {
    NS_WARNING("failed to dispatch executor flush event");
  }
}

void
nsHtml5StreamParser::ParseAvailableData()
{
  NS_ASSERTION(IsParserThread(), "Wrong thread!");
  mTokenizerMutex.AssertCurrentThreadOwns();

  if (IsTerminatedOrInterrupted()) {
    return;
  }

  if (mSpeculating && !IsSpeculationEnabled()) {
    return;
  }

  for (;;) {
    if (!mFirstBuffer->hasMore()) {
      if (mFirstBuffer == mLastBuffer) {
        switch (mStreamState) {
          case STREAM_BEING_READ:
            // never release the last buffer.
            if (!mSpeculating) {
              // reuse buffer space if not speculating
              mFirstBuffer->setStart(0);
              mFirstBuffer->setEnd(0);
            }
            mTreeBuilder->FlushLoads();
            {
              // Dispatch this runnable unconditionally, because the loads
              // that need flushing may have been flushed earlier even if the
              // flush right above here did nothing.
              nsCOMPtr<nsIRunnable> runnable(mLoadFlusher);
              if (NS_FAILED(DispatchToMain(runnable.forget()))) {
                NS_WARNING("failed to dispatch load flush event");
              }
            }
            return; // no more data for now but expecting more
          case STREAM_ENDED:
            if (mAtEOF) {
              return;
            }
            mAtEOF = true;
            if (mCharsetSource < kCharsetFromMetaTag) {
              if (mInitialEncodingWasFromParentFrame) {
                // Unfortunately, this check doesn't take effect for
                // cross-origin frames, so cross-origin ad frames that have
                // no text and only an image or a Flash embed get the more
                // severe message from the next if block. The message is
                // technically accurate, though.
                mTreeBuilder->MaybeComplainAboutCharset(
                  "EncNoDeclarationFrame", false, 0);
              } else if (mMode == NORMAL) {
                mTreeBuilder->MaybeComplainAboutCharset(
                  "EncNoDeclaration", true, 0);
              } else if (mMode == PLAIN_TEXT) {
                mTreeBuilder->MaybeComplainAboutCharset(
                  "EncNoDeclarationPlain", true, 0);
              }
            }
            if (NS_SUCCEEDED(mTreeBuilder->IsBroken())) {
              mTokenizer->eof();
              nsresult rv;
              if (NS_FAILED((rv = mTreeBuilder->IsBroken()))) {
                MarkAsBroken(rv);
              } else {
                mTreeBuilder->StreamEnded();
                if (mMode == VIEW_SOURCE_HTML || mMode == VIEW_SOURCE_XML) {
                  mTokenizer->EndViewSource();
                }
              }
            }
            FlushTreeOpsAndDisarmTimer();
            return; // no more data and not expecting more
          default:
            MOZ_ASSERT_UNREACHABLE("It should be impossible to reach this.");
            return;
        }
      }
      mFirstBuffer = mFirstBuffer->next;
      continue;
    }

    // now we have a non-empty buffer
    mFirstBuffer->adjust(mLastWasCR);
    mLastWasCR = false;
    if (mFirstBuffer->hasMore()) {
      if (!mTokenizer->EnsureBufferSpace(mFirstBuffer->getLength())) {
        MarkAsBroken(NS_ERROR_OUT_OF_MEMORY);
        return;
      }
      mLastWasCR = mTokenizer->tokenizeBuffer(mFirstBuffer);
      nsresult rv;
      if (NS_FAILED((rv = mTreeBuilder->IsBroken()))) {
        MarkAsBroken(rv);
        return;
      }
      // At this point, internalEncodingDeclaration() may have called
      // Terminate, but that never happens together with script.
      // Can't assert that here, though, because it's possible that the main
      // thread has called Terminate() while this thread was parsing.
      if (mTreeBuilder->HasScript()) {
        // HasScript() cannot return true if the tree builder is preventing
        // script execution.
        MOZ_ASSERT(mMode == NORMAL);
        mozilla::MutexAutoLock speculationAutoLock(mSpeculationMutex);
        nsHtml5Speculation* speculation =
          new nsHtml5Speculation(mFirstBuffer,
                                 mFirstBuffer->getStart(),
                                 mTokenizer->getLineNumber(),
                                 mTreeBuilder->newSnapshot());
        mTreeBuilder->AddSnapshotToScript(speculation->GetSnapshot(),
                                          speculation->GetStartLineNumber());
        FlushTreeOpsAndDisarmTimer();
        mTreeBuilder->SetOpSink(speculation);
        mSpeculations.AppendElement(speculation); // adopts the pointer
        mSpeculating = true;
      }
      if (IsTerminatedOrInterrupted()) {
        return;
      }
    }
  }
}

class nsHtml5StreamParserContinuation : public Runnable
{
private:
  nsHtml5StreamParserPtr mStreamParser;

public:
  explicit nsHtml5StreamParserContinuation(nsHtml5StreamParser* aStreamParser)
    : Runnable("nsHtml5StreamParserContinuation")
    , mStreamParser(aStreamParser)
  {
  }
  NS_IMETHOD Run() override
  {
    mozilla::MutexAutoLock autoLock(mStreamParser->mTokenizerMutex);
    mStreamParser->Uninterrupt();
    mStreamParser->ParseAvailableData();
    return NS_OK;
  }
};

void
nsHtml5StreamParser::ContinueAfterScripts(nsHtml5Tokenizer* aTokenizer,
                                          nsHtml5TreeBuilder* aTreeBuilder,
                                          bool aLastWasCR)
{
  NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
  NS_ASSERTION(!(mMode == VIEW_SOURCE_HTML || mMode == VIEW_SOURCE_XML),
               "ContinueAfterScripts called in view source mode!");
  if (NS_FAILED(mExecutor->IsBroken())) {
    return;
  }
#ifdef DEBUG
  mExecutor->AssertStageEmpty();
#endif
  bool speculationFailed = false;
  {
    mozilla::MutexAutoLock speculationAutoLock(mSpeculationMutex);
    if (mSpeculations.IsEmpty()) {
      MOZ_ASSERT_UNREACHABLE("ContinueAfterScripts called without "
                             "speculations.");
      return;
    }

    nsHtml5Speculation* speculation = mSpeculations.ElementAt(0);
    if (aLastWasCR || !aTokenizer->isInDataState() ||
        !aTreeBuilder->snapshotMatches(speculation->GetSnapshot())) {
      speculationFailed = true;
      // We've got a failed speculation :-(
      MaybeDisableFutureSpeculation();
      Interrupt(); // Make the parser thread release the tokenizer mutex sooner
      // now fall out of the speculationAutoLock into the tokenizerAutoLock
      // block
    } else {
      // We've got a successful speculation!
      if (mSpeculations.Length() > 1) {
        // the first speculation isn't the current speculation, so there's
        // no need to bother the parser thread.
        speculation->FlushToSink(mExecutor);
        NS_ASSERTION(!mExecutor->IsScriptExecuting(),
                     "ParseUntilBlocked() was supposed to ensure we don't come "
                     "here when scripts are executing.");
        NS_ASSERTION(
          mExecutor->IsInFlushLoop(),
          "How are we here if "
          "RunFlushLoop() didn't call ParseUntilBlocked() which is the "
          "only caller of this method?");
        mSpeculations.RemoveElementAt(0);
        return;
      }
      // else
      Interrupt(); // Make the parser thread release the tokenizer mutex sooner

      // now fall through
      // the first speculation is the current speculation. Need to
      // release the the speculation mutex and acquire the tokenizer
      // mutex. (Just acquiring the other mutex here would deadlock)
    }
  }
  {
    mozilla::MutexAutoLock tokenizerAutoLock(mTokenizerMutex);
#ifdef DEBUG
    {
      mAtomTable.SetPermittedLookupEventTarget(
        GetMainThreadSerialEventTarget());
    }
#endif
    // In principle, the speculation mutex should be acquired here,
    // but there's no point, because the parser thread only acquires it
    // when it has also acquired the tokenizer mutex and we are already
    // holding the tokenizer mutex.
    if (speculationFailed) {
      // Rewind the stream
      mAtEOF = false;
      nsHtml5Speculation* speculation = mSpeculations.ElementAt(0);
      mFirstBuffer = speculation->GetBuffer();
      mFirstBuffer->setStart(speculation->GetStart());
      mTokenizer->setLineNumber(speculation->GetStartLineNumber());

      nsContentUtils::ReportToConsole(nsIScriptError::warningFlag,
                                      NS_LITERAL_CSTRING("DOM Events"),
                                      mExecutor->GetDocument(),
                                      nsContentUtils::eDOM_PROPERTIES,
                                      "SpeculationFailed",
                                      nullptr,
                                      0,
                                      nullptr,
                                      EmptyString(),
                                      speculation->GetStartLineNumber());

      nsHtml5OwningUTF16Buffer* buffer = mFirstBuffer->next;
      while (buffer) {
        buffer->setStart(0);
        buffer = buffer->next;
      }

      mSpeculations.Clear(); // potentially a huge number of destructors
                             // run here synchronously on the main thread...

      mTreeBuilder->flushCharacters(); // empty the pending buffer
      mTreeBuilder->ClearOps();        // now get rid of the failed ops

      mTreeBuilder->SetOpSink(mExecutor->GetStage());
      mExecutor->StartReadingFromStage();
      mSpeculating = false;

      // Copy state over
      mLastWasCR = aLastWasCR;
      mTokenizer->loadState(aTokenizer);
      mTreeBuilder->loadState(aTreeBuilder, &mAtomTable);
    } else {
      // We've got a successful speculation and at least a moment ago it was
      // the current speculation
      mSpeculations.ElementAt(0)->FlushToSink(mExecutor);
      NS_ASSERTION(!mExecutor->IsScriptExecuting(),
                   "ParseUntilBlocked() was supposed to ensure we don't come "
                   "here when scripts are executing.");
      NS_ASSERTION(
        mExecutor->IsInFlushLoop(),
        "How are we here if "
        "RunFlushLoop() didn't call ParseUntilBlocked() which is the "
        "only caller of this method?");
      mSpeculations.RemoveElementAt(0);
      if (mSpeculations.IsEmpty()) {
        // yes, it was still the only speculation. Now stop speculating
        // However, before telling the executor to read from stage, flush
        // any pending ops straight to the executor, because otherwise
        // they remain unflushed until we get more data from the network.
        mTreeBuilder->SetOpSink(mExecutor);
        mTreeBuilder->Flush(true);
        mTreeBuilder->SetOpSink(mExecutor->GetStage());
        mExecutor->StartReadingFromStage();
        mSpeculating = false;
      }
    }
    nsCOMPtr<nsIRunnable> event = new nsHtml5StreamParserContinuation(this);
    if (NS_FAILED(mEventTarget->Dispatch(event, nsIThread::DISPATCH_NORMAL))) {
      NS_WARNING("Failed to dispatch nsHtml5StreamParserContinuation");
    }
// A stream event might run before this event runs, but that's harmless.
#ifdef DEBUG
    mAtomTable.SetPermittedLookupEventTarget(mEventTarget);
#endif
  }
}

void
nsHtml5StreamParser::ContinueAfterFailedCharsetSwitch()
{
  NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
  nsCOMPtr<nsIRunnable> event = new nsHtml5StreamParserContinuation(this);
  if (NS_FAILED(mEventTarget->Dispatch(event, nsIThread::DISPATCH_NORMAL))) {
    NS_WARNING("Failed to dispatch nsHtml5StreamParserContinuation");
  }
}

class nsHtml5TimerKungFu : public Runnable
{
private:
  nsHtml5StreamParserPtr mStreamParser;

public:
  explicit nsHtml5TimerKungFu(nsHtml5StreamParser* aStreamParser)
    : Runnable("nsHtml5TimerKungFu")
    , mStreamParser(aStreamParser)
  {
  }
  NS_IMETHOD Run() override
  {
    mozilla::MutexAutoLock flushTimerLock(mStreamParser->mFlushTimerMutex);
    if (mStreamParser->mFlushTimer) {
      mStreamParser->mFlushTimer->Cancel();
      mStreamParser->mFlushTimer = nullptr;
    }
    return NS_OK;
  }
};

void
nsHtml5StreamParser::DropTimer()
{
  NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
  /*
   * Simply nulling out the timer wouldn't work, because if the timer is
   * armed, it needs to be canceled first. Simply canceling it first wouldn't
   * work, because nsTimerImpl::Cancel is not safe for calling from outside
   * the thread where nsTimerImpl::Fire would run. It's not safe to
   * dispatch a runnable to cancel the timer from the destructor of this
   * class, because the timer has a weak (void*) pointer back to this instance
   * of the stream parser and having the timer fire before the runnable
   * cancels it would make the timer access a deleted object.
   *
   * This DropTimer method addresses these issues. This method must be called
   * on the main thread before the destructor of this class is reached.
   * The nsHtml5TimerKungFu object has an nsHtml5StreamParserPtr that addrefs
   * this
   * stream parser object to keep it alive until the runnable is done.
   * The runnable cancels the timer on the parser thread, drops the timer
   * and lets nsHtml5StreamParserPtr send a runnable back to the main thread to
   * release the stream parser.
   */
  mozilla::MutexAutoLock flushTimerLock(mFlushTimerMutex);
  if (mFlushTimer) {
    nsCOMPtr<nsIRunnable> event = new nsHtml5TimerKungFu(this);
    if (NS_FAILED(mEventTarget->Dispatch(event, nsIThread::DISPATCH_NORMAL))) {
      NS_WARNING("Failed to dispatch TimerKungFu event");
    }
  }
}

// Using a static, because the method name Notify is taken by the chardet
// callback.
void
nsHtml5StreamParser::TimerCallback(nsITimer* aTimer, void* aClosure)
{
  (static_cast<nsHtml5StreamParser*>(aClosure))->TimerFlush();
}

void
nsHtml5StreamParser::TimerFlush()
{
  NS_ASSERTION(IsParserThread(), "Wrong thread!");
  mozilla::MutexAutoLock autoLock(mTokenizerMutex);

  NS_ASSERTION(!mSpeculating, "Flush timer fired while speculating.");

  // The timer fired if we got here. No need to cancel it. Mark it as
  // not armed, though.
  mFlushTimerArmed = false;

  mFlushTimerEverFired = true;

  if (IsTerminatedOrInterrupted()) {
    return;
  }

  if (mMode == VIEW_SOURCE_HTML || mMode == VIEW_SOURCE_XML) {
    mTreeBuilder->Flush(); // delete useless ops
    if (mTokenizer->FlushViewSource()) {
      nsCOMPtr<nsIRunnable> runnable(mExecutorFlusher);
      if (NS_FAILED(DispatchToMain(runnable.forget()))) {
        NS_WARNING("failed to dispatch executor flush event");
      }
    }
  } else {
    // we aren't speculating and we don't know when new data is
    // going to arrive. Send data to the main thread.
    if (mTreeBuilder->Flush(true)) {
      nsCOMPtr<nsIRunnable> runnable(mExecutorFlusher);
      if (NS_FAILED(DispatchToMain(runnable.forget()))) {
        NS_WARNING("failed to dispatch executor flush event");
      }
    }
  }
}

void
nsHtml5StreamParser::MarkAsBroken(nsresult aRv)
{
  NS_ASSERTION(IsParserThread(), "Wrong thread!");
  mTokenizerMutex.AssertCurrentThreadOwns();

  Terminate();
  mTreeBuilder->MarkAsBroken(aRv);
  mozilla::DebugOnly<bool> hadOps = mTreeBuilder->Flush(false);
  NS_ASSERTION(hadOps, "Should have had the markAsBroken op!");
  nsCOMPtr<nsIRunnable> runnable(mExecutorFlusher);
  if (NS_FAILED(DispatchToMain(runnable.forget()))) {
    NS_WARNING("failed to dispatch executor flush event");
  }
}

nsresult
nsHtml5StreamParser::DispatchToMain(already_AddRefed<nsIRunnable>&& aRunnable)
{
  if (mDocGroup) {
    return mDocGroup->Dispatch(TaskCategory::Network, std::move(aRunnable));
  }
  return SchedulerGroup::UnlabeledDispatch(TaskCategory::Network,
                                           std::move(aRunnable));
}