Rewrite Text node attaching to not be N^2

Source/core/html/parser/HTMLDocumentParser.cpp

Index: Source/core/html/parser/HTMLDocumentParser.cpp
diff --git a/Source/core/html/parser/HTMLDocumentParser.cpp b/Source/core/html/parser/HTMLDocumentParser.cpp
index f61fb4efe6d3c6cbd885cd534be857ab3ed9d713..843fe0fde958f1bf179877f5bc8888c89c7485d4 100644
--- a/Source/core/html/parser/HTMLDocumentParser.cpp
+++ b/Source/core/html/parser/HTMLDocumentParser.cpp
@@ -557,6 +557,9 @@ void HTMLDocumentParser::pumpTokenizer(SynchronousMode mode)
     if (isStopped())
         return;
 
+    if (mode == ForceSynchronous)
+        m_treeBuilder->flush();

[abarth-chromium, 2013/10/11 18:54:04]

Don't you need to check 

if (isStopped())
    return;

here?  It's possible that flushing the tree builder executed JavaScript which
detached the parser.  We don't want to do anything else if that's the case.

+
     if (session.needsYield)
         m_parserScheduler->scheduleForResume();