Revert of Revert of HTMLConstructionSite: avoid n^2 running time for large scripts.

Source/core/html/parser/HTMLTreeBuilder.cpp

 /*
  * Copyright (C) 2010 Google, Inc. All Rights Reserved.
  * Copyright (C) 2011, 2014 Apple 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
@@ skipping 384 matching lines @@
 
 void HTMLTreeBuilder::processToken(AtomicHTMLToken* token)
 {
     if (token->type() == HTMLToken::Character) {
         processCharacter(token);
         return;
     }
 
     // Any non-character token needs to cause us to flush any pending text immediately.
     // NOTE: flush() can cause any queued tasks to execute, possibly re-entering the parser.
-    m_tree.flush();
+    m_tree.flush(FlushAlways);
     m_shouldSkipLeadingNewline = false;
 
     switch (token->type()) {
     case HTMLToken::Uninitialized:
     case HTMLToken::Character:
         ASSERT_NOT_REACHED();
         break;
     case HTMLToken::DOCTYPE:
         processDoctypeToken(token);
         break;
@@ skipping 2266 matching lines @@
 void HTMLTreeBuilder::processTokenInForeignContent(AtomicHTMLToken* token)
 {
     if (token->type() == HTMLToken::Character) {
         const String& characters = token->characters();
         m_tree.insertTextNode(characters);
         if (m_framesetOk && !isAllWhitespaceOrReplacementCharacters(characters))
             m_framesetOk = false;
         return;
     }
 
-    m_tree.flush();
+    m_tree.flush(FlushAlways);
     HTMLStackItem* adjustedCurrentNode = adjustedCurrentStackItem();
 
     switch (token->type()) {
     case HTMLToken::Uninitialized:
         ASSERT_NOT_REACHED();
         break;
     case HTMLToken::DOCTYPE:
         parseError(token);
         break;
     case HTMLToken::StartTag: {
@@ skipping 102 matching lines @@
     ASSERT(m_isAttached);
     // Warning, this may detach the parser. Do not do anything else after this.
     m_tree.finishedParsing();
 }
 
 void HTMLTreeBuilder::parseError(AtomicHTMLToken*)
 {
 }
 
 } // namespace blink