devtools: Treat session history traversal like a navigation.

components/constellation/constellation.rs

@@ -112,7 +112,10 @@ use compositing::compositor_thread::Msg as ToCompositorMsg;
 use compositing::compositor_thread::WebrenderMsg;
 use compositing::{ConstellationMsg as FromCompositorMsg, SendableFrameTree};
 use crossbeam_channel::{after, never, unbounded, Receiver, Sender};
-use devtools_traits::{ChromeToDevtoolsControlMsg, DevtoolsControlMsg};
+use devtools_traits::{
+    ChromeToDevtoolsControlMsg, DevtoolsControlMsg, DevtoolsPageInfo, NavigationState,
+    ScriptToDevtoolsControlMsg,
+};
 use embedder_traits::{Cursor, EmbedderMsg, EmbedderProxy, EventLoopWaker};
 use embedder_traits::{MediaSessionEvent, MediaSessionPlaybackState};
 use euclid::{default::Size2D as UntypedSize2D, Size2D};
@@ -1934,6 +1937,11 @@ where
                 BrowsingContextId::from(source_top_ctx_id),
                 FromScriptMsg::GetWebGPUChan(sender),
             ),
+            FromScriptMsg::TitleChanged(pipeline, title) => {
+                if let Some(pipeline) = self.pipelines.get_mut(&pipeline) {
+                    pipeline.title = title;
+                }
+            },
         }
     }
 
@@ -3935,6 +3943,21 @@ where
             old_pipeline.notify_visibility(false);
         }
         if let Some(new_pipeline) = self.pipelines.get(&new_pipeline_id) {
+            if let Some(ref chan) = self.devtools_chan {
+                let state = NavigationState::Start(new_pipeline.url.clone());
+                let _ = chan.send(DevtoolsControlMsg::FromScript(
+                    ScriptToDevtoolsControlMsg::Navigate(browsing_context_id, state),
+                ));
+                let page_info = DevtoolsPageInfo {
+                    title: new_pipeline.title.clone(),
+                    url: new_pipeline.url.clone(),
+                };
+                let state = NavigationState::Stop(new_pipeline.id, page_info);
+                let _ = chan.send(DevtoolsControlMsg::FromScript(
+                    ScriptToDevtoolsControlMsg::Navigate(browsing_context_id, state),
+                ));
+            }
+
             new_pipeline.notify_visibility(true);
         }
 

components/constellation/pipeline.rs

@@ -97,6 +97,9 @@ pub struct Pipeline {
 
     /// Has this pipeline received a notification that it is completely loaded?
     pub completely_loaded: bool,
+
+    /// The title of this pipeline's document.
+    pub title: String,
 }
 
 /// Initial setup data needed to construct a pipeline.
@@ -379,6 +382,7 @@ impl Pipeline {
             history_state_id: None,
             history_states: HashSet::new(),
             completely_loaded: false,
+            title: String::new(),
         };
 
         pipeline.notify_visibility(is_visible);

components/script/dom/document.rs

@@ -1142,9 +1142,13 @@ impl Document {
     pub fn title_changed(&self) {
         if self.browsing_context().is_some() {
             self.send_title_to_embedder();
+            let title = String::from(self.Title());
+            self.window.send_to_constellation(ScriptMsg::TitleChanged(
+                self.window.pipeline_id(),
+                title.clone(),
+            ));
             let global = self.window.upcast::<GlobalScope>();
             if let Some(ref chan) = global.devtools_chan() {
-                let title = String::from(self.Title());
                 let _ = chan.send(ScriptToDevtoolsControlMsg::TitleChanged(
                     global.pipeline_id(),
                     title,

components/script_traits/script_msg.rs

@@ -282,6 +282,8 @@ pub enum ScriptMsg {
     ),
     /// Get WebGPU channel
     GetWebGPUChan(IpcSender<WebGPU>),
+    /// Notify the constellation of a pipeline's document's title.
+    TitleChanged(PipelineId, String),
 }
 
 impl fmt::Debug for ScriptMsg {
@@ -341,6 +343,7 @@ impl fmt::Debug for ScriptMsg {
             MediaSessionEvent(..) => "MediaSessionEvent",
             RequestAdapter(..) => "RequestAdapter",
             GetWebGPUChan(..) => "GetWebGPUChan",
+            TitleChanged(..) => "TitleChanged",
         };
         write!(formatter, "ScriptMsg::{}", variant)
     }