Fix debug messages

Address other comments

Remove duplicate popstate event binding

components/constellation/constellation.rs

@@ -678,12 +678,12 @@ impl<Message, LTF, STF> Constellation<Message, LTF, STF>
             }
             // Handle request for history length
             Request::Script(FromScriptMsg::HistoryLength(sender)) => {
-                debug!("constellation got history length message from compositor");
+                debug!("constellation got history length message from script");
                 self.handle_history_length(sender);
             }
             // Handle pushing a history entry due to state change
             Request::Script(FromScriptMsg::HistoryStatePushed(pipeline_info, active_index)) => {
-                debug!("constellation got history length message from compositor");
+                debug!("constellation got history state pushed message from script");
                 self.handle_history_state_pushed(pipeline_info, active_index);
             }
             // Notification that the new document is ready to become active

components/script/dom/bindings/global.rs

@@ -199,7 +199,7 @@ impl<'a> GlobalRef<'a> {
         }
     }
 
-    /// `ScriptChan` used to send messages to the event loop of this global's
+    /// `TaskSource` used to queue history taversal messages to the event loop of this global's
     /// thread.
     pub fn history_traversal_task_source(&self) -> Box<TaskSource<HistoryTraversalTask> + Send> {
         match *self {

components/script/dom/window.rs

@@ -605,9 +605,6 @@ impl WindowMethods for Window {
     // https://html.spec.whatwg.org/multipage/#windoweventhandlers
     window_event_handlers!();
 
-    // https://html.spec.whatwg.org/multipage/#handler-window-onpopstate
-    event_handler!(popstate, GetOnpopstate, SetOnpopstate);
-
     // https://developer.mozilla.org/en-US/docs/Web/API/Window/screen
     fn Screen(&self) -> Root<Screen> {
         self.screen.or_init(|| Screen::new(self))