third_party/WebKit/Source/core/html/parser/BackgroundHTMLParser.cpp - chromium/src - Git at Google

 /*
  * Copyright (C) 2013 Google, Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY GOOGLE INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL GOOGLE INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "core/html/parser/BackgroundHTMLParser.h"

 #include "core/HTMLNames.h"
 #include "core/html/parser/HTMLDocumentParser.h"
 #include "core/html/parser/TextResourceDecoder.h"
 #include "core/html/parser/XSSAuditor.h"
 #include "platform/CrossThreadFunctional.h"
 #include "platform/Histogram.h"
 #include "platform/TraceEvent.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebTaskRunner.h"
 #include "wtf/CurrentTime.h"
 #include "wtf/PtrUtil.h"
 #include "wtf/text/TextPosition.h"
 #include <memory>

 namespace blink {

 // On a network with high latency and high bandwidth, using a device
 // with a fast CPU, we could end up speculatively tokenizing
 // the whole document, well ahead of when the main-thread actually needs it.
 // This is a waste of memory (and potentially time if the speculation fails).
 // So we limit our outstanding tokens arbitrarily to 10,000.
 // Our maximal memory spent speculating will be approximately:
 // (defaultOutstandingTokenLimit + defaultPendingTokenLimit) *
 //     sizeof(CompactToken)
 // We use a separate low and high water mark to avoid constantly topping
 // off the main thread's token buffer.
 // At time of writing, this is (10000 + 1000) * 28 bytes = ~308kb of memory.
 // These numbers have not been tuned.
 static const size_t defaultOutstandingTokenLimit = 10000;

 // We limit our chucks to 1000 tokens, to make sure the main
 // thread is never waiting on the parser thread for tokens.
 // This was tuned in https://bugs.webkit.org/show_bug.cgi?id=110408.
 static const size_t defaultPendingTokenLimit = 1000;

 using namespace HTMLNames;

 #if ENABLE(ASSERT)

 static void checkThatTokensAreSafeToSendToAnotherThread(const CompactHTMLTokenStream* tokens)
 {
     for (size_t i = 0; i < tokens->size(); ++i)
         ASSERT(tokens->at(i).isSafeToSendToAnotherThread());
 }

 static void checkThatPreloadsAreSafeToSendToAnotherThread(const PreloadRequestStream& preloads)
 {
     for (size_t i = 0; i < preloads.size(); ++i)
         ASSERT(preloads[i]->isSafeToSendToAnotherThread());
 }

 static void checkThatXSSInfosAreSafeToSendToAnotherThread(const XSSInfoStream& infos)
 {
     for (size_t i = 0; i < infos.size(); ++i)
         ASSERT(infos[i]->isSafeToSendToAnotherThread());
 }

 #endif

 void BackgroundHTMLParser::start(PassRefPtr<WeakReference<BackgroundHTMLParser>> reference, std::unique_ptr<Configuration> config, const KURL& documentURL, std::unique_ptr<CachedDocumentParameters> cachedDocumentParameters, const MediaValuesCached::MediaValuesCachedData& mediaValuesCachedData, std::unique_ptr<WebTaskRunner> loadingTaskRunner)
 {
     new BackgroundHTMLParser(reference, std::move(config), documentURL, std::move(cachedDocumentParameters), mediaValuesCachedData, std::move(loadingTaskRunner));
     // Caller must free by calling stop().
 }

 BackgroundHTMLParser::Configuration::Configuration()
     : outstandingTokenLimit(defaultOutstandingTokenLimit)
     , pendingTokenLimit(defaultPendingTokenLimit)
 {
 }

 BackgroundHTMLParser::BackgroundHTMLParser(PassRefPtr<WeakReference<BackgroundHTMLParser>> reference, std::unique_ptr<Configuration> config, const KURL& documentURL, std::unique_ptr<CachedDocumentParameters> cachedDocumentParameters, const MediaValuesCached::MediaValuesCachedData& mediaValuesCachedData, std::unique_ptr<WebTaskRunner> loadingTaskRunner)
     : m_weakFactory(reference, this)
     , m_token(wrapUnique(new HTMLToken))
     , m_tokenizer(HTMLTokenizer::create(config->options))
     , m_treeBuilderSimulator(config->options)
     , m_options(config->options)
     , m_outstandingTokenLimit(config->outstandingTokenLimit)
     , m_parser(config->parser)
     , m_pendingTokens(wrapUnique(new CompactHTMLTokenStream))
     , m_pendingTokenLimit(config->pendingTokenLimit)
     , m_xssAuditor(std::move(config->xssAuditor))
     , m_preloadScanner(wrapUnique(new TokenPreloadScanner(documentURL, std::move(cachedDocumentParameters), mediaValuesCachedData)))
     , m_decoder(std::move(config->decoder))
     , m_loadingTaskRunner(std::move(loadingTaskRunner))
     , m_parsedChunkQueue(config->parsedChunkQueue.release())
     , m_startingScript(false)
     , m_lastBytesReceivedTime(0.0)
 {
     ASSERT(m_outstandingTokenLimit > 0);
     ASSERT(m_pendingTokenLimit > 0);
     ASSERT(m_outstandingTokenLimit >= m_pendingTokenLimit);
 }

 BackgroundHTMLParser::~BackgroundHTMLParser()
 {
 }

 void BackgroundHTMLParser::appendRawBytesFromMainThread(std::unique_ptr<Vector<char>> buffer, double bytesReceivedTime)
 {
     ASSERT(m_decoder);
     m_lastBytesReceivedTime = bytesReceivedTime;
     DEFINE_STATIC_LOCAL(CustomCountHistogram, queueDelay, ("Parser.AppendBytesDelay", 1, 5000, 50));
     queueDelay.count(monotonicallyIncreasingTimeMS() - bytesReceivedTime);
     updateDocument(m_decoder->decode(buffer->data(), buffer->size()));
 }

 void BackgroundHTMLParser::appendDecodedBytes(const String& input)
 {
     ASSERT(!m_input.current().isClosed());
     m_input.append(input);
     pumpTokenizer();
 }

 void BackgroundHTMLParser::setDecoder(std::unique_ptr<TextResourceDecoder> decoder)
 {
     ASSERT(decoder);
     m_decoder = std::move(decoder);
 }

 void BackgroundHTMLParser::flush()
 {
     ASSERT(m_decoder);
     updateDocument(m_decoder->flush());
 }

 void BackgroundHTMLParser::updateDocument(const String& decodedData)
 {
     DocumentEncodingData encodingData(*m_decoder.get());

     if (encodingData != m_lastSeenEncodingData) {
         m_lastSeenEncodingData = encodingData;

         m_xssAuditor->setEncoding(encodingData.encoding());
         runOnMainThread(crossThreadBind(&HTMLDocumentParser::didReceiveEncodingDataFromBackgroundParser, m_parser, encodingData));
     }

     if (decodedData.isEmpty())
         return;

     appendDecodedBytes(decodedData);
 }

 void BackgroundHTMLParser::resumeFrom(std::unique_ptr<Checkpoint> checkpoint)
 {
     m_parser = checkpoint->parser;
     m_token = std::move(checkpoint->token);
     m_tokenizer = std::move(checkpoint->tokenizer);
     m_treeBuilderSimulator.setState(checkpoint->treeBuilderState);
     m_input.rewindTo(checkpoint->inputCheckpoint, checkpoint->unparsedInput);
     m_preloadScanner->rewindTo(checkpoint->preloadScannerCheckpoint);
     m_startingScript = false;
     m_parsedChunkQueue->clear();
     m_lastBytesReceivedTime = monotonicallyIncreasingTimeMS();
     pumpTokenizer();
 }

 void BackgroundHTMLParser::startedChunkWithCheckpoint(HTMLInputCheckpoint inputCheckpoint)
 {
     // Note, we should not have to worry about the index being invalid
     // as messages from the main thread will be processed in FIFO order.
     m_input.invalidateCheckpointsBefore(inputCheckpoint);
     pumpTokenizer();
 }

 void BackgroundHTMLParser::finish()
 {
     markEndOfFile();
     pumpTokenizer();
 }

 void BackgroundHTMLParser::stop()
 {
     delete this;
 }

 void BackgroundHTMLParser::forcePlaintextForTextDocument()
 {
     // This is only used by the TextDocumentParser (a subclass of HTMLDocumentParser)
     // to force us into the PLAINTEXT state w/o using a <plaintext> tag.
     // The TextDocumentParser uses a <pre> tag for historical/compatibility reasons.
     m_tokenizer->setState(HTMLTokenizer::PLAINTEXTState);
 }

 void BackgroundHTMLParser::markEndOfFile()
 {
     ASSERT(!m_input.current().isClosed());
     m_input.append(String(&kEndOfFileMarker, 1));
     m_input.close();
 }

 void BackgroundHTMLParser::pumpTokenizer()
 {
     TRACE_EVENT0("loading", "BackgroundHTMLParser::pumpTokenizer");
     HTMLTreeBuilderSimulator::SimulatedToken simulatedToken = HTMLTreeBuilderSimulator::OtherToken;

     // No need to start speculating until the main thread has almost caught up.
     if (m_input.totalCheckpointTokenCount() > m_outstandingTokenLimit)
         return;

     while (true) {
         if (m_xssAuditor->isEnabled())
             m_sourceTracker.start(m_input.current(), m_tokenizer.get(), *m_token);

         if (!m_tokenizer->nextToken(m_input.current(), *m_token)) {
             // We've reached the end of our current input.
             sendTokensToMainThread();
             break;
         }

         if (m_xssAuditor->isEnabled())
             m_sourceTracker.end(m_input.current(), m_tokenizer.get(), *m_token);

         {
             TextPosition position = TextPosition(m_input.current().currentLine(), m_input.current().currentColumn());

             if (std::unique_ptr<XSSInfo> xssInfo = m_xssAuditor->filterToken(FilterTokenRequest(*m_token, m_sourceTracker, m_tokenizer->shouldAllowCDATA()))) {
                 xssInfo->m_textPosition = position;
                 m_pendingXSSInfos.append(std::move(xssInfo));
             }

             CompactHTMLToken token(m_token.get(), position);

             bool shouldEvaluateForDocumentWrite = false;
             m_preloadScanner->scan(token, m_input.current(), m_pendingPreloads, &m_viewportDescription, &shouldEvaluateForDocumentWrite);

             simulatedToken = m_treeBuilderSimulator.simulate(token, m_tokenizer.get());

             // Break chunks before a script tag is inserted and flag the chunk as starting a script
             // so the main parser can decide if it should yield before processing the chunk.
             if (simulatedToken == HTMLTreeBuilderSimulator::ScriptStart) {
                 sendTokensToMainThread();
                 m_startingScript = true;
             }

             m_pendingTokens->append(token);
             if (shouldEvaluateForDocumentWrite) {
                 m_likelyDocumentWriteScriptIndices.append(m_pendingTokens->size() - 1);
             }
         }

         m_token->clear();

         if (simulatedToken == HTMLTreeBuilderSimulator::ScriptEnd || m_pendingTokens->size() >= m_pendingTokenLimit) {
             sendTokensToMainThread();
             // If we're far ahead of the main thread, yield for a bit to avoid consuming too much memory.
             if (m_input.totalCheckpointTokenCount() > m_outstandingTokenLimit)
                 break;
         }
     }
 }

 void BackgroundHTMLParser::sendTokensToMainThread()
 {
     if (m_pendingTokens->isEmpty())
         return;

 #if ENABLE(ASSERT)
     checkThatTokensAreSafeToSendToAnotherThread(m_pendingTokens.get());
     checkThatPreloadsAreSafeToSendToAnotherThread(m_pendingPreloads);
     checkThatXSSInfosAreSafeToSendToAnotherThread(m_pendingXSSInfos);
 #endif

     double chunkStartTime = monotonicallyIncreasingTimeMS();
     std::unique_ptr<HTMLDocumentParser::ParsedChunk> chunk = wrapUnique(new HTMLDocumentParser::ParsedChunk);
     TRACE_EVENT_WITH_FLOW0("blink,loading", "BackgroundHTMLParser::sendTokensToMainThread", chunk.get(), TRACE_EVENT_FLAG_FLOW_OUT);

     if (!m_pendingPreloads.isEmpty()) {
         double delay = monotonicallyIncreasingTimeMS() - m_lastBytesReceivedTime;
         DEFINE_STATIC_LOCAL(CustomCountHistogram, preloadTokenizeDelay, ("Parser.PreloadTokenizeDelay", 1, 10000, 50));
         preloadTokenizeDelay.count(delay);
     }

     chunk->preloads.swap(m_pendingPreloads);
     if (m_viewportDescription.set)
         chunk->viewport = m_viewportDescription;
     chunk->xssInfos.swap(m_pendingXSSInfos);
     chunk->tokenizerState = m_tokenizer->getState();
     chunk->treeBuilderState = m_treeBuilderSimulator.state();
     chunk->inputCheckpoint = m_input.createCheckpoint(m_pendingTokens->size());
     chunk->preloadScannerCheckpoint = m_preloadScanner->createCheckpoint();
     chunk->tokens = std::move(m_pendingTokens);
     chunk->startingScript = m_startingScript;
     chunk->likelyDocumentWriteScriptIndices.swap(m_likelyDocumentWriteScriptIndices);
     m_startingScript = false;

     bool isEmpty = m_parsedChunkQueue->enqueue(std::move(chunk));

     DEFINE_STATIC_LOCAL(CustomCountHistogram, chunkEnqueueTime, ("Parser.ChunkEnqueueTime", 1, 10000, 50));
     chunkEnqueueTime.count(monotonicallyIncreasingTimeMS() - chunkStartTime);

     if (isEmpty) {
         runOnMainThread(crossThreadBind(&HTMLDocumentParser::notifyPendingParsedChunks, m_parser));
     }

     m_pendingTokens = wrapUnique(new CompactHTMLTokenStream);
 }

 // If the background parser is already running on the main thread, then it is
 // not necessary to post a task to the main thread to run asynchronously. The
 // main parser deals with chunking up its own work.
 // TODO(csharrison): This is a pretty big hack because we don't actually need a
 // CrossThreadClosure in these cases. This is just experimental.
 void BackgroundHTMLParser::runOnMainThread(std::unique_ptr<CrossThreadClosure> closure)
 {
     if (isMainThread())
         (*closure)();
     else
         m_loadingTaskRunner->postTask(BLINK_FROM_HERE, std::move(closure));
 }

 } // namespace blink
	/*
	* Copyright (C) 2013 Google, Inc. All Rights Reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY GOOGLE INC. ``AS IS'' AND ANY
	* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
	* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GOOGLE INC. OR
	* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
	* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
	* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
	* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
	* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "core/html/parser/BackgroundHTMLParser.h"

	#include "core/HTMLNames.h"
	#include "core/html/parser/HTMLDocumentParser.h"
	#include "core/html/parser/TextResourceDecoder.h"
	#include "core/html/parser/XSSAuditor.h"
	#include "platform/CrossThreadFunctional.h"
	#include "platform/Histogram.h"
	#include "platform/TraceEvent.h"
	#include "public/platform/Platform.h"
	#include "public/platform/WebTaskRunner.h"
	#include "wtf/CurrentTime.h"
	#include "wtf/PtrUtil.h"
	#include "wtf/text/TextPosition.h"
	#include <memory>

	namespace blink {

	// On a network with high latency and high bandwidth, using a device
	// with a fast CPU, we could end up speculatively tokenizing
	// the whole document, well ahead of when the main-thread actually needs it.
	// This is a waste of memory (and potentially time if the speculation fails).
	// So we limit our outstanding tokens arbitrarily to 10,000.
	// Our maximal memory spent speculating will be approximately:
	// (defaultOutstandingTokenLimit + defaultPendingTokenLimit) *
	// sizeof(CompactToken)
	// We use a separate low and high water mark to avoid constantly topping
	// off the main thread's token buffer.
	// At time of writing, this is (10000 + 1000) * 28 bytes = ~308kb of memory.
	// These numbers have not been tuned.
	static const size_t defaultOutstandingTokenLimit = 10000;

	// We limit our chucks to 1000 tokens, to make sure the main
	// thread is never waiting on the parser thread for tokens.
	// This was tuned in https://bugs.webkit.org/show_bug.cgi?id=110408.
	static const size_t defaultPendingTokenLimit = 1000;

	using namespace HTMLNames;

	#if ENABLE(ASSERT)

	static void checkThatTokensAreSafeToSendToAnotherThread(const CompactHTMLTokenStream* tokens)
	{
	for (size_t i = 0; i < tokens->size(); ++i)
	ASSERT(tokens->at(i).isSafeToSendToAnotherThread());
	}

	static void checkThatPreloadsAreSafeToSendToAnotherThread(const PreloadRequestStream& preloads)
	{
	for (size_t i = 0; i < preloads.size(); ++i)
	ASSERT(preloads[i]->isSafeToSendToAnotherThread());
	}

	static void checkThatXSSInfosAreSafeToSendToAnotherThread(const XSSInfoStream& infos)
	{
	for (size_t i = 0; i < infos.size(); ++i)
	ASSERT(infos[i]->isSafeToSendToAnotherThread());
	}

	#endif

	void BackgroundHTMLParser::start(PassRefPtr<WeakReference<BackgroundHTMLParser>> reference, std::unique_ptr<Configuration> config, const KURL& documentURL, std::unique_ptr<CachedDocumentParameters> cachedDocumentParameters, const MediaValuesCached::MediaValuesCachedData& mediaValuesCachedData, std::unique_ptr<WebTaskRunner> loadingTaskRunner)
	{
	new BackgroundHTMLParser(reference, std::move(config), documentURL, std::move(cachedDocumentParameters), mediaValuesCachedData, std::move(loadingTaskRunner));
	// Caller must free by calling stop().
	}

	BackgroundHTMLParser::Configuration::Configuration()
	: outstandingTokenLimit(defaultOutstandingTokenLimit)
	, pendingTokenLimit(defaultPendingTokenLimit)
	{
	}

	BackgroundHTMLParser::BackgroundHTMLParser(PassRefPtr<WeakReference<BackgroundHTMLParser>> reference, std::unique_ptr<Configuration> config, const KURL& documentURL, std::unique_ptr<CachedDocumentParameters> cachedDocumentParameters, const MediaValuesCached::MediaValuesCachedData& mediaValuesCachedData, std::unique_ptr<WebTaskRunner> loadingTaskRunner)
	: m_weakFactory(reference, this)
	, m_token(wrapUnique(new HTMLToken))
	, m_tokenizer(HTMLTokenizer::create(config->options))
	, m_treeBuilderSimulator(config->options)
	, m_options(config->options)
	, m_outstandingTokenLimit(config->outstandingTokenLimit)
	, m_parser(config->parser)
	, m_pendingTokens(wrapUnique(new CompactHTMLTokenStream))
	, m_pendingTokenLimit(config->pendingTokenLimit)
	, m_xssAuditor(std::move(config->xssAuditor))
	, m_preloadScanner(wrapUnique(new TokenPreloadScanner(documentURL, std::move(cachedDocumentParameters), mediaValuesCachedData)))
	, m_decoder(std::move(config->decoder))
	, m_loadingTaskRunner(std::move(loadingTaskRunner))
	, m_parsedChunkQueue(config->parsedChunkQueue.release())
	, m_startingScript(false)
	, m_lastBytesReceivedTime(0.0)
	{
	ASSERT(m_outstandingTokenLimit > 0);
	ASSERT(m_pendingTokenLimit > 0);
	ASSERT(m_outstandingTokenLimit >= m_pendingTokenLimit);
	}

	BackgroundHTMLParser::~BackgroundHTMLParser()
	{
	}

	void BackgroundHTMLParser::appendRawBytesFromMainThread(std::unique_ptr<Vector<char>> buffer, double bytesReceivedTime)
	{
	ASSERT(m_decoder);
	m_lastBytesReceivedTime = bytesReceivedTime;
	DEFINE_STATIC_LOCAL(CustomCountHistogram, queueDelay, ("Parser.AppendBytesDelay", 1, 5000, 50));
	queueDelay.count(monotonicallyIncreasingTimeMS() - bytesReceivedTime);
	updateDocument(m_decoder->decode(buffer->data(), buffer->size()));
	}

	void BackgroundHTMLParser::appendDecodedBytes(const String& input)
	{
	ASSERT(!m_input.current().isClosed());
	m_input.append(input);
	pumpTokenizer();
	}

	void BackgroundHTMLParser::setDecoder(std::unique_ptr<TextResourceDecoder> decoder)
	{
	ASSERT(decoder);
	m_decoder = std::move(decoder);
	}

	void BackgroundHTMLParser::flush()
	{
	ASSERT(m_decoder);
	updateDocument(m_decoder->flush());
	}

	void BackgroundHTMLParser::updateDocument(const String& decodedData)
	{
	DocumentEncodingData encodingData(*m_decoder.get());

	if (encodingData != m_lastSeenEncodingData) {
	m_lastSeenEncodingData = encodingData;

	m_xssAuditor->setEncoding(encodingData.encoding());
	runOnMainThread(crossThreadBind(&HTMLDocumentParser::didReceiveEncodingDataFromBackgroundParser, m_parser, encodingData));
	}

	if (decodedData.isEmpty())
	return;

	appendDecodedBytes(decodedData);
	}

	void BackgroundHTMLParser::resumeFrom(std::unique_ptr<Checkpoint> checkpoint)
	{
	m_parser = checkpoint->parser;
	m_token = std::move(checkpoint->token);
	m_tokenizer = std::move(checkpoint->tokenizer);
	m_treeBuilderSimulator.setState(checkpoint->treeBuilderState);
	m_input.rewindTo(checkpoint->inputCheckpoint, checkpoint->unparsedInput);
	m_preloadScanner->rewindTo(checkpoint->preloadScannerCheckpoint);
	m_startingScript = false;
	m_parsedChunkQueue->clear();
	m_lastBytesReceivedTime = monotonicallyIncreasingTimeMS();
	pumpTokenizer();
	}

	void BackgroundHTMLParser::startedChunkWithCheckpoint(HTMLInputCheckpoint inputCheckpoint)
	{
	// Note, we should not have to worry about the index being invalid
	// as messages from the main thread will be processed in FIFO order.
	m_input.invalidateCheckpointsBefore(inputCheckpoint);
	pumpTokenizer();
	}

	void BackgroundHTMLParser::finish()
	{
	markEndOfFile();
	pumpTokenizer();
	}

	void BackgroundHTMLParser::stop()
	{
	delete this;
	}

	void BackgroundHTMLParser::forcePlaintextForTextDocument()
	{
	// This is only used by the TextDocumentParser (a subclass of HTMLDocumentParser)
	// to force us into the PLAINTEXT state w/o using a <plaintext> tag.
	// The TextDocumentParser uses a <pre> tag for historical/compatibility reasons.
	m_tokenizer->setState(HTMLTokenizer::PLAINTEXTState);
	}

	void BackgroundHTMLParser::markEndOfFile()
	{
	ASSERT(!m_input.current().isClosed());
	m_input.append(String(&kEndOfFileMarker, 1));
	m_input.close();
	}

	void BackgroundHTMLParser::pumpTokenizer()
	{
	TRACE_EVENT0("loading", "BackgroundHTMLParser::pumpTokenizer");
	HTMLTreeBuilderSimulator::SimulatedToken simulatedToken = HTMLTreeBuilderSimulator::OtherToken;

	// No need to start speculating until the main thread has almost caught up.
	if (m_input.totalCheckpointTokenCount() > m_outstandingTokenLimit)
	return;

	while (true) {
	if (m_xssAuditor->isEnabled())
	m_sourceTracker.start(m_input.current(), m_tokenizer.get(), *m_token);

	if (!m_tokenizer->nextToken(m_input.current(), *m_token)) {
	// We've reached the end of our current input.
	sendTokensToMainThread();
	break;
	}

	if (m_xssAuditor->isEnabled())
	m_sourceTracker.end(m_input.current(), m_tokenizer.get(), *m_token);

	{
	TextPosition position = TextPosition(m_input.current().currentLine(), m_input.current().currentColumn());

	if (std::unique_ptr<XSSInfo> xssInfo = m_xssAuditor->filterToken(FilterTokenRequest(*m_token, m_sourceTracker, m_tokenizer->shouldAllowCDATA()))) {
	xssInfo->m_textPosition = position;
	m_pendingXSSInfos.append(std::move(xssInfo));
	}

	CompactHTMLToken token(m_token.get(), position);

	bool shouldEvaluateForDocumentWrite = false;
	m_preloadScanner->scan(token, m_input.current(), m_pendingPreloads, &m_viewportDescription, &shouldEvaluateForDocumentWrite);

	simulatedToken = m_treeBuilderSimulator.simulate(token, m_tokenizer.get());

	// Break chunks before a script tag is inserted and flag the chunk as starting a script
	// so the main parser can decide if it should yield before processing the chunk.
	if (simulatedToken == HTMLTreeBuilderSimulator::ScriptStart) {
	sendTokensToMainThread();
	m_startingScript = true;
	}

	m_pendingTokens->append(token);
	if (shouldEvaluateForDocumentWrite) {
	m_likelyDocumentWriteScriptIndices.append(m_pendingTokens->size() - 1);
	}
	}

	m_token->clear();

	if (simulatedToken == HTMLTreeBuilderSimulator::ScriptEnd \|\| m_pendingTokens->size() >= m_pendingTokenLimit) {
	sendTokensToMainThread();
	// If we're far ahead of the main thread, yield for a bit to avoid consuming too much memory.
	if (m_input.totalCheckpointTokenCount() > m_outstandingTokenLimit)
	break;
	}
	}
	}

	void BackgroundHTMLParser::sendTokensToMainThread()
	{
	if (m_pendingTokens->isEmpty())
	return;

	#if ENABLE(ASSERT)
	checkThatTokensAreSafeToSendToAnotherThread(m_pendingTokens.get());
	checkThatPreloadsAreSafeToSendToAnotherThread(m_pendingPreloads);
	checkThatXSSInfosAreSafeToSendToAnotherThread(m_pendingXSSInfos);
	#endif

	double chunkStartTime = monotonicallyIncreasingTimeMS();
	std::unique_ptr<HTMLDocumentParser::ParsedChunk> chunk = wrapUnique(new HTMLDocumentParser::ParsedChunk);
	TRACE_EVENT_WITH_FLOW0("blink,loading", "BackgroundHTMLParser::sendTokensToMainThread", chunk.get(), TRACE_EVENT_FLAG_FLOW_OUT);

	if (!m_pendingPreloads.isEmpty()) {
	double delay = monotonicallyIncreasingTimeMS() - m_lastBytesReceivedTime;
	DEFINE_STATIC_LOCAL(CustomCountHistogram, preloadTokenizeDelay, ("Parser.PreloadTokenizeDelay", 1, 10000, 50));
	preloadTokenizeDelay.count(delay);
	}

	chunk->preloads.swap(m_pendingPreloads);
	if (m_viewportDescription.set)
	chunk->viewport = m_viewportDescription;
	chunk->xssInfos.swap(m_pendingXSSInfos);
	chunk->tokenizerState = m_tokenizer->getState();
	chunk->treeBuilderState = m_treeBuilderSimulator.state();
	chunk->inputCheckpoint = m_input.createCheckpoint(m_pendingTokens->size());
	chunk->preloadScannerCheckpoint = m_preloadScanner->createCheckpoint();
	chunk->tokens = std::move(m_pendingTokens);
	chunk->startingScript = m_startingScript;
	chunk->likelyDocumentWriteScriptIndices.swap(m_likelyDocumentWriteScriptIndices);
	m_startingScript = false;

	bool isEmpty = m_parsedChunkQueue->enqueue(std::move(chunk));

	DEFINE_STATIC_LOCAL(CustomCountHistogram, chunkEnqueueTime, ("Parser.ChunkEnqueueTime", 1, 10000, 50));
	chunkEnqueueTime.count(monotonicallyIncreasingTimeMS() - chunkStartTime);

	if (isEmpty) {
	runOnMainThread(crossThreadBind(&HTMLDocumentParser::notifyPendingParsedChunks, m_parser));
	}

	m_pendingTokens = wrapUnique(new CompactHTMLTokenStream);
	}

	// If the background parser is already running on the main thread, then it is
	// not necessary to post a task to the main thread to run asynchronously. The
	// main parser deals with chunking up its own work.
	// TODO(csharrison): This is a pretty big hack because we don't actually need a
	// CrossThreadClosure in these cases. This is just experimental.
	void BackgroundHTMLParser::runOnMainThread(std::unique_ptr<CrossThreadClosure> closure)
	{
	if (isMainThread())
	(*closure)();
	else
	m_loadingTaskRunner->postTask(BLINK_FROM_HERE, std::move(closure));
	}

	} // namespace blink