nsHtml5TreeOpExecutor.cpp

/* -*- 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 "mozilla/DebugOnly.h"
#include "mozilla/Likely.h"
#include "mozilla/dom/nsCSPService.h"
#include "mozilla/dom/ScriptLoader.h"

#include "nsError.h"
#include "nsHtml5TreeOpExecutor.h"
#include "nsIContentViewer.h"
#include "nsIContentSecurityPolicy.h"
#include "nsIDocShellTreeItem.h"
#include "nsIDocShell.h"
#include "nsIDOMDocument.h"
#include "nsIScriptGlobalObject.h"
#include "nsIWebShellServices.h"
#include "nsContentUtils.h"
#include "mozAutoDocUpdate.h"
#include "nsNetUtil.h"
#include "nsHtml5Parser.h"
#include "nsHtml5Tokenizer.h"
#include "nsHtml5TreeBuilder.h"
#include "nsHtml5StreamParser.h"
#include "mozilla/css/Loader.h"
#include "GeckoProfiler.h"
#include "nsIScriptError.h"
#include "nsIScriptContext.h"
#include "mozilla/Preferences.h"
#include "nsIHTMLDocument.h"
#include "nsIViewSourceChannel.h"
#include "xpcpublic.h"

using namespace mozilla;

NS_INTERFACE_TABLE_HEAD_CYCLE_COLLECTION_INHERITED(nsHtml5TreeOpExecutor)
  NS_INTERFACE_TABLE_INHERITED(nsHtml5TreeOpExecutor,
                               nsIContentSink)
NS_INTERFACE_TABLE_TAIL_INHERITING(nsHtml5DocumentBuilder)

NS_IMPL_ADDREF_INHERITED(nsHtml5TreeOpExecutor, nsContentSink)

NS_IMPL_RELEASE_INHERITED(nsHtml5TreeOpExecutor, nsContentSink)

class nsHtml5ExecutorReflusher : public Runnable
{
  private:
    RefPtr<nsHtml5TreeOpExecutor> mExecutor;
  public:
    explicit nsHtml5ExecutorReflusher(nsHtml5TreeOpExecutor* aExecutor)
      : mozilla::Runnable("nsHtml5ExecutorReflusher")
      , mExecutor(aExecutor)
    {}
    NS_IMETHOD Run() override
    {
      mExecutor->RunFlushLoop();
      return NS_OK;
    }
};

static mozilla::LinkedList<nsHtml5TreeOpExecutor>* gBackgroundFlushList = nullptr;
static nsITimer* gFlushTimer = nullptr;

nsHtml5TreeOpExecutor::nsHtml5TreeOpExecutor()
  : nsHtml5DocumentBuilder(false)
  , mSuppressEOF(false)
  , mReadingFromStage(false)
  , mStreamParser(nullptr)
  , mPreloadedURLs(23)  // Mean # of preloadable resources per page on dmoz
  , mSpeculationReferrerPolicy(mozilla::net::RP_Unset)
  , mStarted(false)
  , mRunFlushLoopOnStack(false)
  , mCallContinueInterruptedParsingIfEnabled(false)
  , mAlreadyComplainedAboutCharset(false)
{
}

nsHtml5TreeOpExecutor::~nsHtml5TreeOpExecutor()
{
  if (gBackgroundFlushList && isInList()) {
    mOpQueue.Clear();
    removeFrom(*gBackgroundFlushList);
    if (gBackgroundFlushList->isEmpty()) {
      delete gBackgroundFlushList;
      gBackgroundFlushList = nullptr;
      if (gFlushTimer) {
        gFlushTimer->Cancel();
        NS_RELEASE(gFlushTimer);
      }
    }
  }
  NS_ASSERTION(mOpQueue.IsEmpty(), "Somehow there's stuff in the op queue.");
}

// nsIContentSink
NS_IMETHODIMP
nsHtml5TreeOpExecutor::WillParse()
{
  NS_NOTREACHED("No one should call this");
  return NS_ERROR_NOT_IMPLEMENTED;
}

NS_IMETHODIMP
nsHtml5TreeOpExecutor::WillBuildModel(nsDTDMode aDTDMode)
{
  mDocument->AddObserver(this);
  WillBuildModelImpl();
  GetDocument()->BeginLoad();
  if (mDocShell && !GetDocument()->GetWindow() &&
      !IsExternalViewSource()) {
    // Not loading as data but script global object not ready
    return MarkAsBroken(NS_ERROR_DOM_INVALID_STATE_ERR);
  }
  return NS_OK;
}


// This is called when the tree construction has ended
NS_IMETHODIMP
nsHtml5TreeOpExecutor::DidBuildModel(bool aTerminated)
{
  if (!aTerminated) {
    // This is needed to avoid unblocking loads too many times on one hand
    // and on the other hand to avoid destroying the frame constructor from
    // within an update batch. See bug 537683.
    EndDocUpdate();
    
    // If the above caused a call to nsIParser::Terminate(), let that call
    // win.
    if (!mParser) {
      return NS_OK;
    }
  }
  
  if (mRunsToCompletion) {
    return NS_OK;
  }

  GetParser()->DropStreamParser();

  // This comes from nsXMLContentSink and nsHTMLContentSink
  // If this parser has been marked as broken, treat the end of parse as
  // forced termination.
  DidBuildModelImpl(aTerminated || NS_FAILED(IsBroken()));

  if (!mLayoutStarted) {
    // We never saw the body, and layout never got started. Force
    // layout *now*, to get an initial reflow.

    // NOTE: only force the layout if we are NOT destroying the
    // docshell. If we are destroying it, then starting layout will
    // likely cause us to crash, or at best waste a lot of time as we
    // are just going to tear it down anyway.
    bool destroying = true;
    if (mDocShell) {
      mDocShell->IsBeingDestroyed(&destroying);
    }

    if (!destroying) {
      nsContentSink::StartLayout(false);
    }
  }

  ScrollToRef();
  mDocument->RemoveObserver(this);
  if (!mParser) {
    // DidBuildModelImpl may cause mParser to be nulled out
    // Return early to avoid unblocking the onload event too many times.
    return NS_OK;
  }

  // We may not have called BeginLoad() if loading is terminated before
  // OnStartRequest call.
  if (mStarted) {
    mDocument->EndLoad();
  }
  DropParserAndPerfHint();
#ifdef GATHER_DOCWRITE_STATISTICS
  printf("UNSAFE SCRIPTS: %d\n", sUnsafeDocWrites);
  printf("TOKENIZER-SAFE SCRIPTS: %d\n", sTokenSafeDocWrites);
  printf("TREEBUILDER-SAFE SCRIPTS: %d\n", sTreeSafeDocWrites);
#endif
#ifdef DEBUG_NS_HTML5_TREE_OP_EXECUTOR_FLUSH
  printf("MAX NOTIFICATION BATCH LEN: %d\n", sAppendBatchMaxSize);
  if (sAppendBatchExaminations != 0) {
    printf("AVERAGE SLOTS EXAMINED: %d\n", sAppendBatchSlotsExamined / sAppendBatchExaminations);
  }
#endif
  return NS_OK;
}

NS_IMETHODIMP
nsHtml5TreeOpExecutor::WillInterrupt()
{
  NS_NOTREACHED("Don't call. For interface compat only.");
  return NS_ERROR_NOT_IMPLEMENTED;
}

NS_IMETHODIMP
nsHtml5TreeOpExecutor::WillResume()
{
  NS_NOTREACHED("Don't call. For interface compat only.");
  return NS_ERROR_NOT_IMPLEMENTED;
}

NS_IMETHODIMP
nsHtml5TreeOpExecutor::SetParser(nsParserBase* aParser)
{
  mParser = aParser;
  return NS_OK;
}

void
nsHtml5TreeOpExecutor::FlushPendingNotifications(FlushType aType)
{
  if (aType >= FlushType::EnsurePresShellInitAndFrames) {
    // Bug 577508 / 253951
    nsContentSink::StartLayout(true);
  }
}

nsISupports*
nsHtml5TreeOpExecutor::GetTarget()
{
  return mDocument;
}

nsresult
nsHtml5TreeOpExecutor::MarkAsBroken(nsresult aReason)
{
  NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");
  mBroken = aReason;
  if (mStreamParser) {
    mStreamParser->Terminate();
  }
  // We are under memory pressure, but let's hope the following allocation
  // works out so that we get to terminate and clean up the parser from
  // a safer point.
  if (mParser && mDocument) { // can mParser ever be null here?
    nsCOMPtr<nsIRunnable> terminator =
      NewRunnableMethod("nsHtml5Parser::Terminate", GetParser(), &nsHtml5Parser::Terminate);
    if (NS_FAILED(mDocument->Dispatch("nsHtml5Parser::Terminate",
                                      TaskCategory::Network,
                                      terminator.forget()))) {
      NS_WARNING("failed to dispatch executor flush event");
    }
  }
  return aReason;
}

void
FlushTimerCallback(nsITimer* aTimer, void* aClosure)
{
  RefPtr<nsHtml5TreeOpExecutor> ex = gBackgroundFlushList->popFirst();
  if (ex) {
    ex->RunFlushLoop();
  }
  if (gBackgroundFlushList && gBackgroundFlushList->isEmpty()) {
    delete gBackgroundFlushList;
    gBackgroundFlushList = nullptr;
    gFlushTimer->Cancel();
    NS_RELEASE(gFlushTimer);
  }
}

void
nsHtml5TreeOpExecutor::ContinueInterruptedParsingAsync()
{
  if (!mDocument || !mDocument->IsInBackgroundWindow()) {
    nsCOMPtr<nsIRunnable> flusher = new nsHtml5ExecutorReflusher(this);
    if (NS_FAILED(mDocument->Dispatch("nsHtml5ExecutorReflusher",
                                      TaskCategory::Network,
                                      flusher.forget()))) {
      NS_WARNING("failed to dispatch executor flush event");
    }
  } else {
    if (!gBackgroundFlushList) {
      gBackgroundFlushList = new mozilla::LinkedList<nsHtml5TreeOpExecutor>();
    }
    if (!isInList()) {
      gBackgroundFlushList->insertBack(this);
    }
    if (!gFlushTimer) {
      nsCOMPtr<nsITimer> t = do_CreateInstance("@mozilla.org/timer;1");
      t.swap(gFlushTimer);
      // The timer value 50 should not hopefully slow down background pages too
      // much, yet lets event loop to process enough between ticks.
      // See bug 734015.
      gFlushTimer->InitWithNamedFuncCallback(FlushTimerCallback, nullptr,
                                             50, nsITimer::TYPE_REPEATING_SLACK,
                                             "FlushTimerCallback");
    }
  }
}

void
nsHtml5TreeOpExecutor::FlushSpeculativeLoads()
{
  nsTArray<nsHtml5SpeculativeLoad> speculativeLoadQueue;
  mStage.MoveSpeculativeLoadsTo(speculativeLoadQueue);
  const nsHtml5SpeculativeLoad* start = speculativeLoadQueue.Elements();
  const nsHtml5SpeculativeLoad* end = start + speculativeLoadQueue.Length();
  for (nsHtml5SpeculativeLoad* iter = const_cast<nsHtml5SpeculativeLoad*>(start);
       iter < end;
       ++iter) {
    if (MOZ_UNLIKELY(!mParser)) {
      // An extension terminated the parser from a HTTP observer.
      return;
    }
    iter->Perform(this);
  }
}

class nsHtml5FlushLoopGuard
{
  private:
    RefPtr<nsHtml5TreeOpExecutor> mExecutor;
    #ifdef DEBUG_NS_HTML5_TREE_OP_EXECUTOR_FLUSH
    uint32_t mStartTime;
    #endif
  public:
    explicit nsHtml5FlushLoopGuard(nsHtml5TreeOpExecutor* aExecutor)
      : mExecutor(aExecutor)
    #ifdef DEBUG_NS_HTML5_TREE_OP_EXECUTOR_FLUSH
      , mStartTime(PR_IntervalToMilliseconds(PR_IntervalNow()))
    #endif
    {
      mExecutor->mRunFlushLoopOnStack = true;
    }
    ~nsHtml5FlushLoopGuard()
    {
      #ifdef DEBUG_NS_HTML5_TREE_OP_EXECUTOR_FLUSH
        uint32_t timeOffTheEventLoop = 
          PR_IntervalToMilliseconds(PR_IntervalNow()) - mStartTime;
        if (timeOffTheEventLoop > 
            nsHtml5TreeOpExecutor::sLongestTimeOffTheEventLoop) {
          nsHtml5TreeOpExecutor::sLongestTimeOffTheEventLoop = 
            timeOffTheEventLoop;
        }
        printf("Longest time off the event loop: %d\n", 
          nsHtml5TreeOpExecutor::sLongestTimeOffTheEventLoop);
      #endif

      mExecutor->mRunFlushLoopOnStack = false;
    }
};

/**
 * The purpose of the loop here is to avoid returning to the main event loop
 */
void
nsHtml5TreeOpExecutor::RunFlushLoop()
{
  AUTO_PROFILER_LABEL("nsHtml5TreeOpExecutor::RunFlushLoop", OTHER);

  if (mRunFlushLoopOnStack) {
    // There's already a RunFlushLoop() on the call stack.
    return;
  }
  
  nsHtml5FlushLoopGuard guard(this); // this is also the self-kungfu!
  
  RefPtr<nsParserBase> parserKungFuDeathGrip(mParser);

  // Remember the entry time
  (void) nsContentSink::WillParseImpl();

  for (;;) {
    if (!mParser) {
      // Parse has terminated.
      mOpQueue.Clear(); // clear in order to be able to assert in destructor
      return;
    }

    if (NS_FAILED(IsBroken())) {
      return;
    }

    if (!parserKungFuDeathGrip->IsParserEnabled()) {
      // The parser is blocked.
      return;
    }
  
    if (mFlushState != eNotFlushing) {
      // XXX Can this happen? In case it can, let's avoid crashing.
      return;
    }
    
    // If there are scripts executing, then the content sink is jumping the gun
    // (probably due to a synchronous XMLHttpRequest) and will re-enable us
    // later, see bug 460706.
    if (IsScriptExecuting()) {
      return;
    }

    if (mReadingFromStage) {
      nsTArray<nsHtml5SpeculativeLoad> speculativeLoadQueue;
      mStage.MoveOpsAndSpeculativeLoadsTo(mOpQueue, speculativeLoadQueue);
      // Make sure speculative loads never start after the corresponding
      // normal loads for the same URLs.
      const nsHtml5SpeculativeLoad* start = speculativeLoadQueue.Elements();
      const nsHtml5SpeculativeLoad* end = start + speculativeLoadQueue.Length();
      for (nsHtml5SpeculativeLoad* iter = (nsHtml5SpeculativeLoad*)start;
           iter < end;
           ++iter) {
        iter->Perform(this);
        if (MOZ_UNLIKELY(!mParser)) {
          // An extension terminated the parser from a HTTP observer.
          mOpQueue.Clear(); // clear in order to be able to assert in destructor
          return;
        }
      }
    } else {
      FlushSpeculativeLoads(); // Make sure speculative loads never start after
                               // the corresponding normal loads for the same
                               // URLs.
      if (MOZ_UNLIKELY(!mParser)) {
        // An extension terminated the parser from a HTTP observer.
        mOpQueue.Clear(); // clear in order to be able to assert in destructor
        return;
      }
      // Not sure if this grip is still needed, but previously, the code
      // gripped before calling ParseUntilBlocked();
      RefPtr<nsHtml5StreamParser> streamKungFuDeathGrip = 
        GetParser()->GetStreamParser();
      mozilla::Unused << streamKungFuDeathGrip; // Not used within function
      // Now parse content left in the document.write() buffer queue if any.
      // This may generate tree ops on its own or dequeue a speculation.
      nsresult rv = GetParser()->ParseUntilBlocked();
      if (NS_FAILED(rv)) {
        MarkAsBroken(rv);
        return;
      }
    }

    if (mOpQueue.IsEmpty()) {
      // Avoid bothering the rest of the engine with a doc update if there's 
      // nothing to do.
      return;
    }

    mFlushState = eInFlush;

    nsIContent* scriptElement = nullptr;
    bool interrupted = false;
    
    BeginDocUpdate();

    uint32_t numberOfOpsToFlush = mOpQueue.Length();

    const nsHtml5TreeOperation* first = mOpQueue.Elements();
    const nsHtml5TreeOperation* last = first + numberOfOpsToFlush - 1;
    for (nsHtml5TreeOperation* iter = const_cast<nsHtml5TreeOperation*>(first);;) {
      if (MOZ_UNLIKELY(!mParser)) {
        // The previous tree op caused a call to nsIParser::Terminate().
        break;
      }
      NS_ASSERTION(mFlushState == eInDocUpdate, 
        "Tried to perform tree op outside update batch.");
      nsresult rv = iter->Perform(this, &scriptElement, &interrupted);
      if (NS_FAILED(rv)) {
        MarkAsBroken(rv);
        break;
      }

      // Be sure not to check the deadline if the last op was just performed.
      if (MOZ_UNLIKELY(iter == last)) {
        break;
      } else if (MOZ_UNLIKELY(interrupted) ||
                 MOZ_UNLIKELY(nsContentSink::DidProcessATokenImpl() ==
                              NS_ERROR_HTMLPARSER_INTERRUPTED)) {
        mOpQueue.RemoveElementsAt(0, (iter - first) + 1);
        
        EndDocUpdate();

        mFlushState = eNotFlushing;

        #ifdef DEBUG_NS_HTML5_TREE_OP_EXECUTOR_FLUSH
          printf("REFLUSH SCHEDULED (executing ops): %d\n", 
            ++sTimesFlushLoopInterrupted);
        #endif
        nsHtml5TreeOpExecutor::ContinueInterruptedParsingAsync();
        return;
      }
      ++iter;
    }
    
    mOpQueue.Clear();
    
    EndDocUpdate();

    mFlushState = eNotFlushing;

    if (MOZ_UNLIKELY(!mParser)) {
      // The parse ended already.
      return;
    }

    if (scriptElement) {
      // must be tail call when mFlushState is eNotFlushing
      RunScript(scriptElement);
      
      // Always check the clock in nsContentSink right after a script
      StopDeflecting();
      if (nsContentSink::DidProcessATokenImpl() == 
          NS_ERROR_HTMLPARSER_INTERRUPTED) {
        #ifdef DEBUG_NS_HTML5_TREE_OP_EXECUTOR_FLUSH
          printf("REFLUSH SCHEDULED (after script): %d\n", 
            ++sTimesFlushLoopInterrupted);
        #endif
        nsHtml5TreeOpExecutor::ContinueInterruptedParsingAsync();
        return;      
      }
    }
  }
}

nsresult
nsHtml5TreeOpExecutor::FlushDocumentWrite()
{
  nsresult rv = IsBroken();
  NS_ENSURE_SUCCESS(rv, rv);

  FlushSpeculativeLoads(); // Make sure speculative loads never start after the
                // corresponding normal loads for the same URLs.

  if (MOZ_UNLIKELY(!mParser)) {
    // The parse has ended.
    mOpQueue.Clear(); // clear in order to be able to assert in destructor
    return rv;
  }
  
  if (mFlushState != eNotFlushing) {
    // XXX Can this happen? In case it can, let's avoid crashing.
    return rv;
  }

  mFlushState = eInFlush;

  // avoid crashing near EOF
  RefPtr<nsHtml5TreeOpExecutor> kungFuDeathGrip(this);
  RefPtr<nsParserBase> parserKungFuDeathGrip(mParser);
  mozilla::Unused << parserKungFuDeathGrip; // Intentionally not used within function

  NS_ASSERTION(!mReadingFromStage,
    "Got doc write flush when reading from stage");

#ifdef DEBUG
  mStage.AssertEmpty();
#endif
  
  nsIContent* scriptElement = nullptr;
  bool interrupted = false;
  
  BeginDocUpdate();

  uint32_t numberOfOpsToFlush = mOpQueue.Length();

  const nsHtml5TreeOperation* start = mOpQueue.Elements();
  const nsHtml5TreeOperation* end = start + numberOfOpsToFlush;
  for (nsHtml5TreeOperation* iter = const_cast<nsHtml5TreeOperation*>(start);
       iter < end;
       ++iter) {
    if (MOZ_UNLIKELY(!mParser)) {
      // The previous tree op caused a call to nsIParser::Terminate().
      break;
    }
    NS_ASSERTION(mFlushState == eInDocUpdate, 
      "Tried to perform tree op outside update batch.");
    rv = iter->Perform(this, &scriptElement, &interrupted);
    if (NS_FAILED(rv)) {
      MarkAsBroken(rv);
      break;
    }
  }

  mOpQueue.Clear();
  
  EndDocUpdate();

  mFlushState = eNotFlushing;

  if (MOZ_UNLIKELY(!mParser)) {
    // Ending the doc update caused a call to nsIParser::Terminate().
    return rv;
  }

  if (scriptElement) {
    // must be tail call when mFlushState is eNotFlushing
    RunScript(scriptElement);
  }
  return rv;
}

// copied from HTML content sink
bool
nsHtml5TreeOpExecutor::IsScriptEnabled()
{
  // Note that if we have no document or no docshell or no global or whatnot we
  // want to claim script _is_ enabled, so we don't parse the contents of
  // <noscript> tags!
  if (!mDocument || !mDocShell)
    return true;
  nsCOMPtr<nsIScriptGlobalObject> globalObject = do_QueryInterface(mDocument->GetInnerWindow());
  // Getting context is tricky if the document hasn't had its
  // GlobalObject set yet
  if (!globalObject) {
    globalObject = mDocShell->GetScriptGlobalObject();
  }
  NS_ENSURE_TRUE(globalObject && globalObject->GetGlobalJSObject(), true);
  return xpc::Scriptability::Get(globalObject->GetGlobalJSObject()).Allowed();
}

void
nsHtml5TreeOpExecutor::StartLayout(bool* aInterrupted) {
  if (mLayoutStarted || !mDocument) {
    return;
  }

  EndDocUpdate();

  if (MOZ_UNLIKELY(!mParser)) {
    // got terminate
    return;
  }

  nsContentSink::StartLayout(false);

  if (mParser) {
    *aInterrupted = !GetParser()->IsParserEnabled();

    BeginDocUpdate();
  }
}

void
nsHtml5TreeOpExecutor::PauseDocUpdate(bool* aInterrupted) {
  // Pausing the document update allows JS to run, and potentially block
  // further parsing.
  EndDocUpdate();

  if (MOZ_LIKELY(mParser)) {
    *aInterrupted = !GetParser()->IsParserEnabled();

    BeginDocUpdate();
  }
}

/**
 * The reason why this code is here and not in the tree builder even in the 
 * main-thread case is to allow the control to return from the tokenizer 
 * before scripts run. This way, the tokenizer is not invoked re-entrantly 
 * although the parser is.
 *
 * The reason why this is called as a tail call when mFlushState is set to
 * eNotFlushing is to allow re-entry to Flush() but only after the current 
 * Flush() has cleared the op queue and is otherwise done cleaning up after 
 * itself.
 */
void
nsHtml5TreeOpExecutor::RunScript(nsIContent* aScriptElement)
{
  if (mRunsToCompletion) {
    // We are in createContextualFragment() or in the upcoming document.parse().
    // Do nothing. Let's not even mark scripts malformed here, because that
    // could cause serialization weirdness later.
    return;
  }

  NS_ASSERTION(aScriptElement, "No script to run");
  nsCOMPtr<nsIScriptElement> sele = do_QueryInterface(aScriptElement);
  if (!sele) {
    MOZ_ASSERT(nsNameSpaceManager::GetInstance()->mSVGDisabled, "Node didn't QI to script, but SVG wasn't disabled.");
    return;
  }
  
  if (!mParser) {
    NS_ASSERTION(sele->IsMalformed(), "Script wasn't marked as malformed.");
    // We got here not because of an end tag but because the tree builder
    // popped an incomplete script element on EOF. Returning here to avoid
    // calling back into mParser anymore.
    return;
  }
  
  if (sele->GetScriptDeferred() || sele->GetScriptAsync()) {
    DebugOnly<bool> block = sele->AttemptToExecute();
    NS_ASSERTION(!block, "Defer or async script tried to block.");
    return;
  }
  
  NS_ASSERTION(mFlushState == eNotFlushing, "Tried to run script when flushing.");

  mReadingFromStage = false;
  
  sele->SetCreatorParser(GetParser());

  // Copied from nsXMLContentSink
  // 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 the act of insertion evaluated the script, we're fine.
  // Else, block the parser till the script has loaded.
  if (block) {
    if (mParser) {
      GetParser()->BlockParser();
    }
  } else {
    // mParser may have been nulled out by now, but the flusher deals

    // If this event isn't needed, it doesn't do anything. It is sometimes
    // necessary for the parse to continue after complex situations.
    nsHtml5TreeOpExecutor::ContinueInterruptedParsingAsync();
  }
}

void
nsHtml5TreeOpExecutor::Start()
{
  NS_PRECONDITION(!mStarted, "Tried to start when already started.");
  mStarted = true;
}

void
nsHtml5TreeOpExecutor::NeedsCharsetSwitchTo(NotNull<const Encoding*> aEncoding,
                                            int32_t aSource,
                                            uint32_t aLineNumber)
{
  EndDocUpdate();

  if (MOZ_UNLIKELY(!mParser)) {
    // got terminate
    return;
  }
  
  nsCOMPtr<nsIWebShellServices> wss = do_QueryInterface(mDocShell);
  if (!wss) {
    return;
  }

  // ask the webshellservice to load the URL
  if (NS_SUCCEEDED(wss->StopDocumentLoad())) {
    nsAutoCString charset;
    aEncoding->Name(charset);
    wss->ReloadDocument(charset.get(), aSource);
  }
  // if the charset switch was accepted, wss has called Terminate() on the
  // parser by now

  if (!mParser) {
    // success
    if (aSource == kCharsetFromMetaTag) {
      MaybeComplainAboutCharset("EncLateMetaReload", false, aLineNumber);
    }
    return;
  }

  if (aSource == kCharsetFromMetaTag) {
    MaybeComplainAboutCharset("EncLateMetaTooLate", true, aLineNumber);
  }

  GetParser()->ContinueAfterFailedCharsetSwitch();

  BeginDocUpdate();
}

void
nsHtml5TreeOpExecutor::MaybeComplainAboutCharset(const char* aMsgId,
                                                 bool aError,
                                                 uint32_t aLineNumber)
{
  if (mAlreadyComplainedAboutCharset) {
    return;
  }
  // The EncNoDeclaration case for advertising iframes is so common that it
  // would result is way too many errors. The iframe case doesn't matter
  // when the ad is an image or a Flash animation anyway. When the ad is
  // textual, a misrendered ad probably isn't a huge loss for users.
  // Let's suppress the message in this case.
  // This means that errors about other different-origin iframes in mashups
  // are lost as well, but generally, the site author isn't in control of
  // the embedded different-origin pages anyway and can't fix problems even
  // if alerted about them.
  if (!strcmp(aMsgId, "EncNoDeclaration") && mDocShell) {
    nsCOMPtr<nsIDocShellTreeItem> parent;
    mDocShell->GetSameTypeParent(getter_AddRefs(parent));
    if (parent) {
      return;
    }
  }
  mAlreadyComplainedAboutCharset = true;
  nsContentUtils::ReportToConsole(aError ? nsIScriptError::errorFlag
                                         : nsIScriptError::warningFlag,
                                  NS_LITERAL_CSTRING("HTML parser"),
                                  mDocument,
                                  nsContentUtils::eHTMLPARSER_PROPERTIES,
                                  aMsgId,
                                  nullptr,
                                  0,
                                  nullptr,
                                  EmptyString(),
                                  aLineNumber);
}

void
nsHtml5TreeOpExecutor::ComplainAboutBogusProtocolCharset(nsIDocument* aDoc)
{
  NS_ASSERTION(!mAlreadyComplainedAboutCharset,
               "How come we already managed to complain?");
  mAlreadyComplainedAboutCharset = true;
  nsContentUtils::ReportToConsole(nsIScriptError::errorFlag,
                                  NS_LITERAL_CSTRING("HTML parser"),
                                  aDoc,
                                  nsContentUtils::eHTMLPARSER_PROPERTIES,
                                  "EncProtocolUnsupported");
}

nsHtml5Parser*
nsHtml5TreeOpExecutor::GetParser()
{
  MOZ_ASSERT(!mRunsToCompletion);
  return static_cast<nsHtml5Parser*>(mParser.get());
}

void
nsHtml5TreeOpExecutor::MoveOpsFrom(nsTArray<nsHtml5TreeOperation>& aOpQueue)
{
  NS_PRECONDITION(mFlushState == eNotFlushing, "mOpQueue modified during tree op execution.");
  mOpQueue.AppendElements(Move(aOpQueue));
}

void
nsHtml5TreeOpExecutor::InitializeDocWriteParserState(nsAHtml5TreeBuilderState* aState, int32_t aLine)
{
  GetParser()->InitializeDocWriteParserState(aState, aLine);
}

nsIURI*
nsHtml5TreeOpExecutor::GetViewSourceBaseURI()
{
  if (!mViewSourceBaseURI) {

    // We query the channel for the baseURI because in certain situations it
    // cannot otherwise be determined. If this process fails, fall back to the
    // standard method.
    nsCOMPtr<nsIViewSourceChannel> vsc =
      do_QueryInterface(mDocument->GetChannel());
    if (vsc) {
      nsresult rv =  vsc->GetBaseURI(getter_AddRefs(mViewSourceBaseURI));
      if (NS_SUCCEEDED(rv) && mViewSourceBaseURI) {
        return mViewSourceBaseURI;
      }
    }

    nsCOMPtr<nsIURI> orig = mDocument->GetOriginalURI();
    bool isViewSource;
    orig->SchemeIs("view-source", &isViewSource);
    if (isViewSource) {
      nsCOMPtr<nsINestedURI> nested = do_QueryInterface(orig);
      NS_ASSERTION(nested, "URI with scheme view-source didn't QI to nested!");
      nested->GetInnerURI(getter_AddRefs(mViewSourceBaseURI));
    } else {
      // Fail gracefully if the base URL isn't a view-source: URL.
      // Not sure if this can ever happen.
      mViewSourceBaseURI = orig;
    }
  }
  return mViewSourceBaseURI;
}

//static
void
nsHtml5TreeOpExecutor::InitializeStatics()
{
  mozilla::Preferences::AddBoolVarCache(&sExternalViewSource,
                                        "view_source.editor.external");
}

bool
nsHtml5TreeOpExecutor::IsExternalViewSource()
{
  if (!sExternalViewSource) {
    return false;
  }
  bool isViewSource = false;
  if (mDocumentURI) {
    mDocumentURI->SchemeIs("view-source", &isViewSource);
  }
  return isViewSource;
}

// Speculative loading

nsIURI*
nsHtml5TreeOpExecutor::BaseURIForPreload()
{
  // The URL of the document without <base>
  nsIURI* documentURI = mDocument->GetDocumentURI();
  // The URL of the document with non-speculative <base>
  nsIURI* documentBaseURI = mDocument->GetDocBaseURI();

  // If the two above are different, use documentBaseURI. If they are the same,
  // the document object isn't aware of a <base>, so attempt to use the
  // mSpeculationBaseURI or, failing, that, documentURI.
  return (documentURI == documentBaseURI) ?
          (mSpeculationBaseURI ?
           mSpeculationBaseURI.get() : documentURI)
         : documentBaseURI;
}

already_AddRefed<nsIURI>
nsHtml5TreeOpExecutor::ConvertIfNotPreloadedYet(const nsAString& aURL)
{
  if (aURL.IsEmpty()) {
    return nullptr;
  }

  nsIURI* base = BaseURIForPreload();
  auto encoding = mDocument->GetDocumentCharacterSet();
  nsCOMPtr<nsIURI> uri;
  nsresult rv = NS_NewURI(getter_AddRefs(uri), aURL, encoding, base);
  if (NS_FAILED(rv)) {
    NS_WARNING("Failed to create a URI");
    return nullptr;
  }

  if (ShouldPreloadURI(uri)) {
    return uri.forget();
  }

  return nullptr;
}

bool
nsHtml5TreeOpExecutor::ShouldPreloadURI(nsIURI *aURI)
{
  nsAutoCString spec;
  nsresult rv = aURI->GetSpec(spec);
  NS_ENSURE_SUCCESS(rv, false);
  return mPreloadedURLs.EnsureInserted(spec);
}

void
nsHtml5TreeOpExecutor::PreloadScript(const nsAString& aURL,
                                     const nsAString& aCharset,
                                     const nsAString& aType,
                                     const nsAString& aCrossOrigin,
                                     const nsAString& aIntegrity,
                                     bool aScriptFromHead)
{
  nsCOMPtr<nsIURI> uri = ConvertIfNotPreloadedYet(aURL);
  if (!uri) {
    return;
  }
  mDocument->ScriptLoader()->PreloadURI(uri, aCharset, aType, aCrossOrigin,
                                           aIntegrity, aScriptFromHead,
                                           mSpeculationReferrerPolicy);
}

void
nsHtml5TreeOpExecutor::PreloadStyle(const nsAString& aURL,
                                    const nsAString& aCharset,
                                    const nsAString& aCrossOrigin,
                                    const nsAString& aIntegrity)
{
  nsCOMPtr<nsIURI> uri = ConvertIfNotPreloadedYet(aURL);
  if (!uri) {
    return;
  }
  mDocument->PreloadStyle(uri, aCharset, aCrossOrigin,
                          mSpeculationReferrerPolicy, aIntegrity);
}

void
nsHtml5TreeOpExecutor::PreloadImage(const nsAString& aURL,
                                    const nsAString& aCrossOrigin,
                                    const nsAString& aSrcset,
                                    const nsAString& aSizes,
                                    const nsAString& aImageReferrerPolicy)
{
  nsCOMPtr<nsIURI> baseURI = BaseURIForPreload();
  nsCOMPtr<nsIURI> uri = mDocument->ResolvePreloadImage(baseURI, aURL, aSrcset,
                                                        aSizes);
  if (uri && ShouldPreloadURI(uri)) {
    // use document wide referrer policy
    mozilla::net::ReferrerPolicy referrerPolicy = mSpeculationReferrerPolicy;
    mozilla::net::ReferrerPolicy imageReferrerPolicy =
      mozilla::net::AttributeReferrerPolicyFromString(aImageReferrerPolicy);
    if (imageReferrerPolicy != mozilla::net::RP_Unset) {
      referrerPolicy = imageReferrerPolicy;
    }

    mDocument->MaybePreLoadImage(uri, aCrossOrigin, referrerPolicy);
  }
}

// These calls inform the document of picture state and seen sources, such that
// it can use them to inform ResolvePreLoadImage as necessary
void
nsHtml5TreeOpExecutor::PreloadPictureSource(const nsAString& aSrcset,
                                            const nsAString& aSizes,
                                            const nsAString& aType,
                                            const nsAString& aMedia)
{
  mDocument->PreloadPictureImageSource(aSrcset, aSizes, aType, aMedia);
}

void
nsHtml5TreeOpExecutor::PreloadOpenPicture()
{
  mDocument->PreloadPictureOpened();
}

void
nsHtml5TreeOpExecutor::PreloadEndPicture()
{
  mDocument->PreloadPictureClosed();
}

void
nsHtml5TreeOpExecutor::AddBase(const nsAString& aURL)
{
  auto encoding = mDocument->GetDocumentCharacterSet();
  nsresult rv = NS_NewURI(getter_AddRefs(mViewSourceBaseURI), aURL,
                          encoding, GetViewSourceBaseURI());
  if (NS_FAILED(rv)) {
    mViewSourceBaseURI = nullptr;
  }
}
void
nsHtml5TreeOpExecutor::SetSpeculationBase(const nsAString& aURL)
{
  if (mSpeculationBaseURI) {
    // the first one wins
    return;
  }
  auto encoding = mDocument->GetDocumentCharacterSet();
  DebugOnly<nsresult> rv = NS_NewURI(getter_AddRefs(mSpeculationBaseURI), aURL,
                                     encoding, mDocument->GetDocumentURI());
  NS_WARNING_ASSERTION(NS_SUCCEEDED(rv), "Failed to create a URI");
}

void
nsHtml5TreeOpExecutor::SetSpeculationReferrerPolicy(const nsAString& aReferrerPolicy)
{
  // Specs says:
  // - Let value be the result of stripping leading and trailing whitespace from
  // the value of element's content attribute.
  // - If value is not the empty string, then:
  if (aReferrerPolicy.IsEmpty()) {
    return;
  }

  ReferrerPolicy policy = mozilla::net::ReferrerPolicyFromString(aReferrerPolicy);
  // Specs says:
  // - If policy is not the empty string, then set element's node document's
  // referrer policy to policy
  if (policy != mozilla::net::RP_Unset) {
    SetSpeculationReferrerPolicy(policy);
  }
}

void
nsHtml5TreeOpExecutor::AddSpeculationCSP(const nsAString& aCSP)
{
  if (!CSPService::sCSPEnabled) {
    return;
  }

  NS_ASSERTION(NS_IsMainThread(), "Wrong thread!");

  nsIPrincipal* principal = mDocument->NodePrincipal();
  nsCOMPtr<nsIContentSecurityPolicy> preloadCsp;
  nsCOMPtr<nsIDOMDocument> domDoc = do_QueryInterface(mDocument);
  nsresult rv = principal->EnsurePreloadCSP(domDoc, getter_AddRefs(preloadCsp));
  NS_ENSURE_SUCCESS_VOID(rv);

  // please note that meta CSPs and CSPs delivered through a header need
  // to be joined together.
  rv = preloadCsp->AppendPolicy(aCSP,
                                false, // csp via meta tag can not be report only
                                true); // delivered through the meta tag
  NS_ENSURE_SUCCESS_VOID(rv);

  // Record "speculated" referrer policy for preloads
  bool hasReferrerPolicy = false;
  uint32_t referrerPolicy = mozilla::net::RP_Unset;
  rv = preloadCsp->GetReferrerPolicy(&referrerPolicy, &hasReferrerPolicy);
  NS_ENSURE_SUCCESS_VOID(rv);
  if (hasReferrerPolicy) {
    SetSpeculationReferrerPolicy(static_cast<ReferrerPolicy>(referrerPolicy));
  }

  mDocument->ApplySettingsFromCSP(true);
}

void
nsHtml5TreeOpExecutor::SetSpeculationReferrerPolicy(ReferrerPolicy aReferrerPolicy)
{
  // Record "speculated" referrer policy locally and thread through the
  // speculation phase.  The actual referrer policy will be set by
  // HTMLMetaElement::BindToTree().
  mSpeculationReferrerPolicy = aReferrerPolicy;
}

#ifdef DEBUG_NS_HTML5_TREE_OP_EXECUTOR_FLUSH
uint32_t nsHtml5TreeOpExecutor::sAppendBatchMaxSize = 0;
uint32_t nsHtml5TreeOpExecutor::sAppendBatchSlotsExamined = 0;
uint32_t nsHtml5TreeOpExecutor::sAppendBatchExaminations = 0;
uint32_t nsHtml5TreeOpExecutor::sLongestTimeOffTheEventLoop = 0;
uint32_t nsHtml5TreeOpExecutor::sTimesFlushLoopInterrupted = 0;
#endif
bool nsHtml5TreeOpExecutor::sExternalViewSource = false;