Fix some of the remove-event-handler problems

components/script/dom/eventtarget.rs

@@ -404,9 +404,15 @@ impl EventTarget {
         });
 
         match idx {
-            Some(idx) => {
-                entries[idx].listener =
-                    EventListenerType::Inline(listener.unwrap_or(InlineEventListener::Null));
+            Some(idx) => match listener {
+                // Replace if there's something to replace with,
+                // but remove entirely if there isn't.
+                Some(listener) => {
+                    entries[idx].listener = EventListenerType::Inline(listener);
+                },
+                None => {
+                    entries.remove(idx);
+                },
             },
             None => {
                 if let Some(listener) = listener {

tests/wpt/metadata/html/webappapis/scripting/events/event-handler-removal.window.js.ini

@@ -1,10 +1,3 @@
 [event-handler-removal.window.html]
   [Event handler set through content attribute should be deactivated when the content attribute is removed.]
     expected: FAIL
-
-  [Event handler set through IDL should be deactivated when the IDL attribute is set to null.]
-    expected: FAIL
-
-  [Event handler set through content attribute should be removed when they are set to null.]
-    expected: FAIL
-