Bug 1092737 followup, because ScalarValueString got renamed.

dom/webidl/TextDecoder.webidl

@@ -18,7 +18,7 @@ interface TextDecoder {
   [Constant]
   readonly attribute boolean fatal;
   [Throws]
-  ScalarValueString decode(optional BufferSource input, optional TextDecodeOptions options);
+  USVString decode(optional BufferSource input, optional TextDecodeOptions options);
 };
 
 dictionary TextDecoderOptions {

dom/webidl/TextEncoder.webidl

@@ -16,5 +16,5 @@ interface TextEncoder {
   [Constant]
   readonly attribute DOMString encoding;
   [Throws, NewObject]
-  Uint8Array encode(optional ScalarValueString input = "");
+  Uint8Array encode(optional USVString input = "");
 };