Document attribute charset and its aliases to return UTF-8

Source/core/dom/Document.idl

Index: Source/core/dom/Document.idl
diff --git a/Source/core/dom/Document.idl b/Source/core/dom/Document.idl
index a27bc8a8b529bb5d5825558646f1f5656b279ed1..50bf456aa1ab93d5f65598cbb1491565c99404d9 100644
--- a/Source/core/dom/Document.idl
+++ b/Source/core/dom/Document.idl
@@ -38,10 +38,9 @@ interface Document : Node {
     [ImplementedAs=url] readonly attribute DOMString? documentURI;
     readonly attribute DOMString origin;
     readonly attribute DOMString compatMode;
-    // FIXME: characterSet should not be nullable.
-    readonly attribute DOMString? characterSet;
-    // FIXME: inputEncoding should not be nullable.
-    [MeasureAs=DocumentInputEncoding, ImplementedAs=characterSet] readonly attribute DOMString? inputEncoding; // legacy alias of .characterSet
+
+    readonly attribute DOMString characterSet;
+    [MeasureAs=DocumentInputEncoding, ImplementedAs=characterSet] readonly attribute DOMString inputEncoding; // legacy alias of .characterSet
     readonly attribute DOMString contentType;
 
     readonly attribute DocumentType? doctype;
@@ -196,8 +195,8 @@ interface Document : Node {
     readonly attribute VisibilityState visibilityState;
 
     // Non-standard APIs
-    [MeasureAs=DocumentCharset, TreatReturnedNullStringAs=Undefined] readonly attribute DOMString charset;
-    [MeasureAs=DocumentDefaultCharset, TreatReturnedNullStringAs=Undefined] readonly attribute DOMString defaultCharset;
+    [MeasureAs=DocumentCharset] readonly attribute DOMString charset;
+    [MeasureAs=DocumentDefaultCharset] readonly attribute DOMString defaultCharset;
     [MeasureAs=DocumentCaretRangeFromPoint] Range caretRangeFromPoint([Default=Undefined] optional long x, [Default=Undefined] optional long y);
     [DeprecateAs=DocumentGetCSSCanvasContext] RenderingContext getCSSCanvasContext(DOMString contextId, DOMString name, long width, long height);