Undeprecate Event.returnValue and Attr.specified

Source/core/frame/UseCounter.cpp

Index: Source/core/frame/UseCounter.cpp
diff --git a/Source/core/frame/UseCounter.cpp b/Source/core/frame/UseCounter.cpp
index f8d9a2a3700008b8a14ed8306fe0087ebba0725a..5246be0e5018337127f4b5a879034eae552d8a8f 100644
--- a/Source/core/frame/UseCounter.cpp
+++ b/Source/core/frame/UseCounter.cpp
@@ -646,18 +646,12 @@ String UseCounter::deprecationMessage(Feature feature)
     case FileError:
         return "FileError is deprecated. Please use the 'name' or 'message' attributes of DOMError rather than 'code'.";
 
-    case EventReturnValue:
-        return "event.returnValue is deprecated. Please use the standard event.preventDefault() instead.";
-
     case ShowModalDialog:
         return "Chromium is considering deprecating showModalDialog. Please use window.open and postMessage instead.";
 
     case CSSStyleSheetInsertRuleOptionalArg:
         return "Calling CSSStyleSheet.insertRule() with one argument is deprecated. Please pass the index argument as well: insertRule(x, 0).";
 
-    case AttributeSpecified:
-        return "Attr.specified is deprecated. Its value is always true.";
-
     case SVGElementGetPresentationAttribute:
         return "CSSValue and SVGElement.getPresentationAttribute are deprecated. Please use getPropertyValue and parse the return value instead.";