Deprecate FileError in FileAPI

Source/core/page/UseCounter.cpp

Index: Source/core/page/UseCounter.cpp
diff --git a/Source/core/page/UseCounter.cpp b/Source/core/page/UseCounter.cpp
index 57f7c0cc9d16ecac674e8ec030856641dcca447e..1d85a3add06cdda94e00832e996babd108af47e3 100644
--- a/Source/core/page/UseCounter.cpp
+++ b/Source/core/page/UseCounter.cpp
@@ -662,6 +662,9 @@ String UseCounter::deprecationMessage(Feature feature)
     case ConsoleMarkTimeline:
         return "console.markTimeline is deprecated. Please use the console.timeStamp instead.";
 
+    case FileError:
+        return "FileError is deprecated. Please use the 'name' or 'message' attributes of DOMError rather than 'code'.";
+
     // Features that aren't deprecated don't have a deprecation message.
     default:
         return String();