Implement request's redirect mode and RequestRedirect for Fetch

Source/modules/fetch/Request.idl

Index: Source/modules/fetch/Request.idl
diff --git a/Source/modules/fetch/Request.idl b/Source/modules/fetch/Request.idl
index 87491b90d227a3e084bfb5fdf3eb726f9650094c..e8124de5e88e4b1ca7cd562d39bda3a99adffd91 100644
--- a/Source/modules/fetch/Request.idl
+++ b/Source/modules/fetch/Request.idl
@@ -15,6 +15,7 @@ enum RequestContext {
 };
 enum RequestMode { "same-origin", "no-cors", "cors" };
 enum RequestCredentials { "omit", "same-origin", "include" };
+enum RequestRedirect { "follow", "error", "manual" };
 
 [
     Constructor(RequestInfo input, optional Dictionary requestInitDict),
@@ -32,6 +33,7 @@ enum RequestCredentials { "omit", "same-origin", "include" };
     readonly attribute DOMString referrer;
     readonly attribute RequestMode mode;
     readonly attribute RequestCredentials credentials;
+    readonly attribute RequestRedirect redirect;
 
     [RaisesException] Request clone();
 };