Bug 1504694 [wpt PR 13920] - XMLHttpRequest: manipulate Content-Type a little more, a=testonly

Automatic update from web-platform-testsXMLHttpRequest: manipulate Content-Type a little more

99f4fdcd906411c036e96c055e28b3e6ca84a1cc was not entirely correct unfortunately.
--

wpt-commits: 47aa8753bba8656899eca2e7c3851a7c75c1d2d7
wpt-pr: 13920

testing/web-platform/tests/xhr/send-content-type-charset.htm

@@ -88,8 +88,12 @@
       )
       request(
         "text/plain;charset= utf-8",
-        "text/plain;charset= utf-8",
-        "charset with space that is UTF-8 does not change")
+        "text/plain;charset=UTF-8",
+        "charset with leading space that is UTF-8 does change")
+      request(
+        "text/plain;charset=utf-8 ;x=x",
+        "text/plain;charset=utf-8 ;x=x",
+        "charset with trailing space that is UTF-8 does not change");
       request(
         "text/plain;charset=\"utf-8\"",
         "text/plain;charset=\"utf-8\"",