Revert of Revert "Moved text decoding to the parser thread"

Source/core/html/parser/HTMLParserIdioms.h

Index: Source/core/html/parser/HTMLParserIdioms.h
diff --git a/Source/core/html/parser/HTMLParserIdioms.h b/Source/core/html/parser/HTMLParserIdioms.h
index 16fd3eebe3cb808dd0252c35a69add4e9e9fb905..49dbed3ba6c6639e80eff7daa5847e36dc3b8b1c 100644
--- a/Source/core/html/parser/HTMLParserIdioms.h
+++ b/Source/core/html/parser/HTMLParserIdioms.h
@@ -30,6 +30,10 @@
 #include "wtf/Forward.h"
 #include "wtf/text/WTFString.h"
 
+namespace WTF {
+class TextEncoding;
+}
+
 namespace WebCore {
 
 // Space characters as defined by the HTML specification.
@@ -61,6 +65,10 @@ bool parseHTMLInteger(const String&, int&);
 // http://www.whatwg.org/specs/web-apps/current-work/#rules-for-parsing-non-negative-integers
 bool parseHTMLNonNegativeInteger(const String&, unsigned int&);
 
+typedef Vector<pair<String, String> > HTMLAttributeList;
+// The returned encoding might not be valid.
+WTF::TextEncoding encodingFromMetaAttributes(const HTMLAttributeList&);
+
 // Inline implementations of some of the functions declared above.
 
 template<typename CharType>