Merge adjacent identical impl sections

Prior to #7416 and #7401, many of these `impl` sections were not
identical

components/script/dom/htmlscriptelement.rs

@@ -503,10 +503,7 @@ impl HTMLScriptElement {
     pub fn mark_already_started(&self) {
         self.already_started.set(true);
     }
-}
 
-
-impl HTMLScriptElement {
     fn dispatch_event(&self,
                       type_: DOMString,
                       bubbles: EventBubbles,