Send WillNavigate earlier during navigation startup (#37778)

The will-navigate message tells the devtools client to expect a
navigation for a browsing context. This makes the network monitor clear
any previous entries and show the requests for the new page that is
loaded. In order to support this correctly, we need to send the
navigation notification from the constellation instead of the script
thread, otherwise we silently ignore navigations triggered by the
browser URL bar.




Testing: Ran servo in devtools mode , now the requests appear for new
loaded page
Fixes: https://github.com/servo/servo/issues/37334

---------

Signed-off-by: Uthman Yahaya Baba <uthmanyahayababa@gmail.com>

components/devtools/lib.rs

@@ -45,6 +45,7 @@ use crate::actors::process::ProcessActor;
 use crate::actors::root::RootActor;
 use crate::actors::source::SourceActor;
 use crate::actors::thread::ThreadActor;
+use crate::actors::watcher::WatcherActor;
 use crate::actors::worker::{WorkerActor, WorkerType};
 use crate::id::IdMap;
 use crate::network_handler::handle_network_event;
@@ -289,11 +290,7 @@ impl DevtoolsInstance {
                         connections.push(stream.try_clone().unwrap());
                     }
 
-                    let pipeline_id = match network_event {
-                        NetworkEvent::HttpResponse(ref response) => response.pipeline_id,
-                        NetworkEvent::HttpRequest(ref request) => request.pipeline_id,
-                    };
-                    self.handle_network_event(connections, pipeline_id, request_id, network_event);
+                    self.handle_network_event(connections, request_id, network_event);
                 },
                 DevtoolsControlMsg::FromChrome(ChromeToDevtoolsControlMsg::ServerExitMsg) => break,
             }
@@ -313,11 +310,23 @@ impl DevtoolsInstance {
 
     fn handle_navigate(&self, browsing_context_id: BrowsingContextId, state: NavigationState) {
         let actor_name = self.browsing_contexts.get(&browsing_context_id).unwrap();
-        self.actors
-            .lock()
-            .unwrap()
-            .find::<BrowsingContextActor>(actor_name)
-            .navigate(state, &mut self.id_map.lock().expect("Mutex poisoned"));
+        let actors = self.actors.lock().unwrap();
+        let actor = actors.find::<BrowsingContextActor>(actor_name);
+        let mut id_map = self.id_map.lock().expect("Mutex poisoned");
+        if let NavigationState::Start(url) = &state {
+            let mut connections = Vec::<TcpStream>::new();
+            for stream in self.connections.values() {
+                connections.push(stream.try_clone().unwrap());
+            }
+            let watcher_actor = actors.find::<WatcherActor>(&actor.watcher);
+            watcher_actor.emit_will_navigate(
+                browsing_context_id,
+                url.clone(),
+                &mut connections,
+                &mut id_map,
+            );
+        };
+        actor.navigate(state, &mut id_map);
     }
 
     // We need separate actor representations for each script global that exists;
@@ -479,31 +488,39 @@ impl DevtoolsInstance {
     fn handle_network_event(
         &mut self,
         connections: Vec<TcpStream>,
-        pipeline_id: PipelineId,
         request_id: String,
         network_event: NetworkEvent,
     ) {
-        let netevent_actor_name = self.find_network_event_actor(request_id);
+        let browsing_context_id = match &network_event {
+            NetworkEvent::HttpRequest(req) => req.browsing_context_id,
+            NetworkEvent::HttpResponse(resp) => resp.browsing_context_id,
+        };
 
-        let Some(id) = self.pipelines.get(&pipeline_id) else {
-            return;
-        };
-        let Some(browsing_context_actor_name) = self.browsing_contexts.get(id) else {
+        let Some(browsing_context_actor_name) = self.browsing_contexts.get(&browsing_context_id)
+        else {
             return;
         };
+        let watcher_name = self
+            .actors
+            .lock()
+            .unwrap()
+            .find::<BrowsingContextActor>(browsing_context_actor_name)
+            .watcher
+            .clone();
+
+        let netevent_actor_name = self.find_network_event_actor(request_id, watcher_name);
 
         handle_network_event(
             Arc::clone(&self.actors),
             netevent_actor_name,
             connections,
             network_event,
-            browsing_context_actor_name.to_string(),
         )
     }
 
     // Find the name of NetworkEventActor corresponding to request_id
     // Create a new one if it does not exist, add it to the actor_requests hashmap
-    fn find_network_event_actor(&mut self, request_id: String) -> String {
+    fn find_network_event_actor(&mut self, request_id: String, watcher_name: String) -> String {
         let mut actors = self.actors.lock().unwrap();
         match self.actor_requests.entry(request_id) {
             Occupied(name) => {
@@ -514,7 +531,7 @@ impl DevtoolsInstance {
                 let resource_id = self.next_resource_id;
                 self.next_resource_id += 1;
                 let actor_name = actors.new_name("netevent");
-                let actor = NetworkEventActor::new(actor_name.clone(), resource_id);
+                let actor = NetworkEventActor::new(actor_name.clone(), resource_id, watcher_name);
                 entry.insert(actor_name.clone());
                 actors.register(Box::new(actor));
                 actor_name