Create MediaValuesCached and TokenPreloadScanner on the parser thread

third_party/WebKit/Source/core/html/parser/HTMLDocumentParser.cpp

 /*
  * Copyright (C) 2010 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
@@ skipping 669 matching lines @@
     RELEASE_ASSERT(!isStopped());
 
     if (isWaitingForScripts()) {
         ASSERT(m_tokenizer->state() == HTMLTokenizer::DataState);
 
         ASSERT(m_preloader);
         // TODO(kouhei): m_preloader should be always available for synchronous parsing case,
         // adding paranoia if for speculative crash fix for crbug.com/465478
         if (m_preloader) {
             if (!m_preloadScanner) {
-                m_preloadScanner = adoptPtr(new HTMLPreloadScanner(m_options,
+                m_preloadScanner = HTMLPreloadScanner::create(
+                    m_options,
                     document()->url(),
-                    CachedDocumentParameters::create(document())));
+                    CachedDocumentParameters::create(document()),
+                    MediaValuesCached::MediaValuesCachedData(*document()));
                 m_preloadScanner->appendToEnd(m_input.current());
             }
             m_preloadScanner->scan(m_preloader.get(), document()->baseElementURL());
         }
     }
 
     TRACE_EVENT_END1("devtools.timeline", "ParseHTML", "endData", InspectorParseHtmlEvent::endData(m_input.current().currentLine().zeroBasedInt() - 1));
 }
 
 void HTMLDocumentParser::constructTreeFromHTMLToken()
@@ skipping 61 matching lines @@
 
     SegmentedString excludedLineNumberSource(source);
     excludedLineNumberSource.setExcludeLineNumbers();
     m_input.insertAtCurrentInsertionPoint(excludedLineNumberSource);
     pumpTokenizerIfPossible();
 
     if (isWaitingForScripts()) {
         // Check the document.write() output with a separate preload scanner as
         // the main scanner can't deal with insertions.
         if (!m_insertionPreloadScanner) {
-            m_insertionPreloadScanner = adoptPtr(new HTMLPreloadScanner(m_options,
+            m_insertionPreloadScanner = HTMLPreloadScanner::create(
+                m_options,
                 document()->url(),
-                CachedDocumentParameters::create(document())));
+                CachedDocumentParameters::create(document()),
+                MediaValuesCached::MediaValuesCachedData(*document()));
         }
 
         m_insertionPreloadScanner->appendToEnd(source);
         m_insertionPreloadScanner->scan(m_preloader.get(), document()->baseElementURL());
     }
 
     endIfDelayed();
 }
 
 void HTMLDocumentParser::startBackgroundParser()
@@ skipping 16 matching lines @@
         if (DocumentLoader* loader = document()->loader())
             loader->attachThreadedDataReceiver(ParserDataReceiver::create(m_backgroundParser, document()->contextDocument().get()));
     }
 
     OwnPtr<BackgroundHTMLParser::Configuration> config = adoptPtr(new BackgroundHTMLParser::Configuration);
     config->options = m_options;
     config->parser = m_weakFactory.createWeakPtr();
     config->xssAuditor = adoptPtr(new XSSAuditor);
     config->xssAuditor->init(document(), &m_xssAuditorDelegate);
 
-    config->preloadScanner = adoptPtr(new TokenPreloadScanner(document()->url().copy(), CachedDocumentParameters::create(document())));
     config->decoder = takeDecoder();
     config->parsedChunkQueue = m_parsedChunkQueue.get();
     if (document()->settings()) {
         if (document()->settings()->backgroundHtmlParserOutstandingTokenLimit())
             config->outstandingTokenLimit = document()->settings()->backgroundHtmlParserOutstandingTokenLimit();
         if (document()->settings()->backgroundHtmlParserPendingTokenLimit())
             config->pendingTokenLimit = document()->settings()->backgroundHtmlParserPendingTokenLimit();
     }
 
     ASSERT(config->xssAuditor->isSafeToSendToAnotherThread());
-    ASSERT(config->preloadScanner->isSafeToSendToAnotherThread());
-    HTMLParserThread::shared()->postTask(threadSafeBind(&BackgroundHTMLParser::start, reference.release(), config.release(),
+    HTMLParserThread::shared()->postTask(threadSafeBind(
+        &BackgroundHTMLParser::start,
+        reference.release(),
+        config.release(),
+        document()->url(),
+        CachedDocumentParameters::create(document()),

[Yoav Weiss, 2016/02/01 09:29:30]

Isn't that racy? IIUC (and it's fairly possible I might not be...)
CachedDocumentParameters::create(document()) and
MediaValuesCachedData(*document()) are run in the context of the background
thread, which means that we're passing document() over.

At least in theory, I don't think that's safe.

[hiroshige, 2016/02/01 09:42:10]

I think:
1. HTMLDocumentParser::startBackgroundParser() is called on the main thread.
2. CachedDocumentParameters::create(document()) and
MediaValuesCachedData(*document()) are also executed on the main thread.
3. Results of Step 2 is processed by CrossThreadCopier, and passed across
threads.
4. BackgroundHTMLParser::start() is executed on the background parser thread.

Because Step 2. is executed on the main thread, I expect this is safe.

+        MediaValuesCached::MediaValuesCachedData(*document()),
         adoptPtr(m_loadingTaskRunner->clone())));
 }
 
 void HTMLDocumentParser::stopBackgroundParser()
 {
     ASSERT(shouldUseThreading());
     ASSERT(m_haveBackgroundParser);
     m_haveBackgroundParser = false;
 
     HTMLParserThread::shared()->postTask(threadSafeBind(&BackgroundHTMLParser::stop, AllowCrossThreadAccess(m_backgroundParser)));
@@ skipping 319 matching lines @@
 void HTMLDocumentParser::setDecoder(PassOwnPtr<TextResourceDecoder> decoder)
 {
     ASSERT(decoder);
     DecodedDataDocumentParser::setDecoder(decoder);
 
     if (m_haveBackgroundParser)
         HTMLParserThread::shared()->postTask(threadSafeBind(&BackgroundHTMLParser::setDecoder, AllowCrossThreadAccess(m_backgroundParser), takeDecoder()));
 }
 
 } // namespace blink