Add support for [TreatNullAs] extended attribute for reflected attributes

Source/core/html/HTMLMediaElement.idl

Index: Source/core/html/HTMLMediaElement.idl
diff --git a/Source/core/html/HTMLMediaElement.idl b/Source/core/html/HTMLMediaElement.idl
index 3cf979387299fe6ffc878c4e41712f517dc7a456..24982058eafb632cdc3c55b1dfd8147bf6352dad 100644
--- a/Source/core/html/HTMLMediaElement.idl
+++ b/Source/core/html/HTMLMediaElement.idl
@@ -32,7 +32,7 @@
 readonly attribute MediaError error;
 
 // network state
-[Reflect, URL] attribute DOMString src;
+[Reflect, TreatNullAs=NullString, URL] attribute DOMString src;
 [URL] readonly attribute DOMString currentSrc;
 
 const unsigned short NETWORK_EMPTY = 0;
@@ -102,6 +102,6 @@ readonly attribute unsigned long webkitVideoDecodedByteCount;
 [EnabledAtRuntime=VideoTrack, RaisesException] TextTrack addTextTrack(DOMString kind, optional DOMString label, optional DOMString language);
 [EnabledAtRuntime=VideoTrack] readonly attribute TextTrackList textTracks;
 
-[Reflect, TreatNullAs=NullString] attribute DOMString mediaGroup;
+[Reflect, TreatNullAs=NullString, TreatNullAs=NullString] attribute DOMString mediaGroup;
 [CustomSetter] attribute MediaController controller;
 };