Turn DocumentParser::pinToMainThread into a cleaner api

Source/core/html/parser/TextDocumentParser.cpp

Index: Source/core/html/parser/TextDocumentParser.cpp
diff --git a/Source/core/html/parser/TextDocumentParser.cpp b/Source/core/html/parser/TextDocumentParser.cpp
index bc7c5b063bfbe2039210449eaa24f1fbad8ac743..4db67fa26453015794b67d5071d5fb543b7ef5e9 100644
--- a/Source/core/html/parser/TextDocumentParser.cpp
+++ b/Source/core/html/parser/TextDocumentParser.cpp
@@ -27,13 +27,14 @@
 
 #include "core/HTMLNames.h"
 #include "core/html/parser/HTMLTreeBuilder.h"
+#include "core/html/parser/ParserSynchronizationPolicy.h"
 
 namespace blink {
 
 using namespace HTMLNames;
 
 TextDocumentParser::TextDocumentParser(HTMLDocument& document)
-    : HTMLDocumentParser(document, false)
+    : HTMLDocumentParser(document, false, AllowAsynchronousParsing)
     , m_haveInsertedFakePreElement(false)
 {
 }