Revert of Make the HTMLDocumentParser yield more aggressively

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 299 matching lines @@
         && document()->frame() && document()->frame()->navigationScheduler().locationChangePending())
         return false;
 
     return true;
 }
 
 void HTMLDocumentParser::didReceiveParsedChunkFromBackgroundParser(PassOwnPtr<ParsedChunk> chunk)
 {
     TRACE_EVENT0("blink", "HTMLDocumentParser::didReceiveParsedChunkFromBackgroundParser");
 
-    if (!isParsing())
+    // alert(), runModalDialog, and the JavaScript Debugger all run nested event loops
+    // which can cause this method to be re-entered. We detect re-entry using
+    // hasActiveParser(), save the chunk as a speculation, and return.
+    if (isWaitingForScripts() || !m_speculations.isEmpty() || document()->activeParserCount() > 0 || m_tasksWereSuspended || isScheduledForResume()) {
+        if (m_tasksWereSuspended)
+            m_parserScheduler->forceResumeAfterYield();
+        m_preloader->takeAndPreload(chunk->preloads);
+        m_speculations.append(chunk);
         return;
-
-    // ApplicationCache needs to be initialized before issuing preloads.
-    // We suspend preload until HTMLHTMLElement is inserted and
-    // ApplicationCache is initialized.
-    if (!document()->documentElement()) {
-        for (auto& request : chunk->preloads)
-            m_queuedPreloads.append(request.release());
-    } else {
-        // We can safely assume that there are no queued preloads request after
-        // the document element is available, as we empty the queue immediately
-        // after the document element is created in pumpPendingSpeculations().
-        ASSERT(m_queuedPreloads.isEmpty());
-        m_preloader->takeAndPreload(chunk->preloads);
     }
 
+    // processParsedChunkFromBackgroundParser can cause this parser to be detached from the Document,
+    // but we need to ensure it isn't deleted yet.
+    RefPtrWillBeRawPtr<HTMLDocumentParser> protect(this);
+
+    ASSERT(m_speculations.isEmpty());
+    chunk->preloads.clear(); // We don't need to preload because we're going to parse immediately.
     m_speculations.append(chunk);
-
-    if (!isWaitingForScripts() && !isScheduledForResume()) {
-        if (m_tasksWereSuspended)
-            m_parserScheduler->forceResumeAfterYield();
-        else
-            m_parserScheduler->scheduleForResume();
-    }
+    pumpPendingSpeculations();
 }
 
 void HTMLDocumentParser::didReceiveEncodingDataFromBackgroundParser(const DocumentEncodingData& data)
 {
     document()->setEncodingData(data);
 }
 
 void HTMLDocumentParser::validateSpeculations(PassOwnPtr<ParsedChunk> chunk)
 {
     ASSERT(chunk);
@@ skipping 97 matching lines @@
                 ASSERT(m_speculations.isEmpty()); // There should never be any chunks after the EOF.
                 prepareToStopParsing();
             }
             break;
         }
 
         m_textPosition = it->textPosition();
 
         constructTreeFromCompactHTMLToken(*it);
 
-        if (!m_queuedPreloads.isEmpty() && document()->documentElement())
-            m_preloader->takeAndPreload(m_queuedPreloads);
-
         if (isStopped())
             break;
 
         if (isWaitingForScripts()) {
             ASSERT(it + 1 == tokens->end()); // The </script> is assumed to be the last token of this bunch.
             runScriptsForPausedTreeBuilder();
             validateSpeculations(chunk.release());
             break;
         }
 
@@ skipping 597 matching lines @@
 void HTMLDocumentParser::setDecoder(PassOwnPtr<TextResourceDecoder> decoder)
 {
     ASSERT(decoder);
     DecodedDataDocumentParser::setDecoder(decoder);
 
     if (m_haveBackgroundParser)
         HTMLParserThread::shared()->postTask(bind(&BackgroundHTMLParser::setDecoder, m_backgroundParser, takeDecoder()));
 }
 
 }