Make Document.inputEncoding an explicit alias of Document.characterSet

Source/core/loader/TextResourceDecoderBuilder.cpp

Index: Source/core/loader/TextResourceDecoderBuilder.cpp
diff --git a/Source/core/loader/TextResourceDecoderBuilder.cpp b/Source/core/loader/TextResourceDecoderBuilder.cpp
index 624873edc914c96f5427ef58825c8902a8dd5d1c..8ce03ae95bca43d0f613c65c71d01d5295503301 100644
--- a/Source/core/loader/TextResourceDecoderBuilder.cpp
+++ b/Source/core/loader/TextResourceDecoderBuilder.cpp
@@ -89,7 +89,7 @@ inline void TextResourceDecoderBuilder::setupEncoding(TextResourceDecoder* decod
             decoder->setHintEncoding(parentFrame->document()->encoding());
 
         if (m_encoding.isEmpty())
-            decoder->setEncoding(parentFrame->document()->inputEncoding().string(), TextResourceDecoder::EncodingFromParentFrame);
+            decoder->setEncoding(parentFrame->document()->encoding(), TextResourceDecoder::EncodingFromParentFrame);
     }
 }