Remove the Document.charset setter (making it readonly)

Source/core/loader/DocumentWriter.cpp

Index: Source/core/loader/DocumentWriter.cpp
diff --git a/Source/core/loader/DocumentWriter.cpp b/Source/core/loader/DocumentWriter.cpp
index 622dc6f37cd0b7feb844ea4b1ce0d8343ef89bd6..f85252ec210207174fdf424589c437afca42dadd 100644
--- a/Source/core/loader/DocumentWriter.cpp
+++ b/Source/core/loader/DocumentWriter.cpp
@@ -119,13 +119,6 @@ void DocumentWriter::end()
     m_document = nullptr;
 }
 
-void DocumentWriter::setUserChosenEncoding(const String& charset)
-{
-    TextResourceDecoder* decoder = m_parser->decoder();
-    if (decoder)
-        decoder->setEncoding(charset, TextResourceDecoder::UserChosenEncoding);
-}
-
 void DocumentWriter::setDocumentWasLoadedAsPartOfNavigation()
 {
     ASSERT(m_parser && !m_parser->isStopped());