delete useThreading flag as it is always true

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 2095 matching lines @@
             // Pause ourselves so that parsing stops until the script can be processed by the caller.
             ASSERT(m_tree.currentStackItem()->hasTagName(scriptTag));
             if (scriptingContentIsAllowed(m_tree.parserContentPolicy()))
                 m_scriptToProcess = m_tree.currentElement();
             m_tree.openElements()->pop();
             setInsertionMode(m_originalInsertionMode);
 
             if (m_parser->tokenizer()) {
                 // We must set the tokenizer's state to
                 // DataState explicitly if the tokenizer didn't have a chance to.
-                ASSERT(m_parser->tokenizer()->state() == HTMLTokenizer::DataState || m_options.useThreading);
                 m_parser->tokenizer()->setState(HTMLTokenizer::DataState);
             }
             return;
         }
         m_tree.openElements()->pop();
         setInsertionMode(m_originalInsertionMode);
         break;
     case InFramesetMode:
         ASSERT(insertionMode() == InFramesetMode);
         if (token->name() == framesetTag) {
@@ skipping 678 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