Auto merge of #22121 - gterzian:remove_constellation_block_in_navigation, r=paulrouget

Remove sync constellation -> embedder communication

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- [ ] `./mach build -d` does not report any errors
- [ ] `./mach test-tidy` does not report any errors
- [ ] These changes fix #22042 (github issue number if applicable).

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components/script_traits/lib.rs

@@ -246,6 +246,10 @@ pub enum UpdatePipelineIdReason {
 /// Messages sent from the constellation or layout to the script thread.
 #[derive(Deserialize, Serialize)]
 pub enum ConstellationControlMsg {
+    /// Takes the associated window proxy out of "delaying-load-events-mode",
+    /// used if a scheduled navigated was refused by the embedder.
+    /// https://html.spec.whatwg.org/multipage/#delaying-load-events-mode
+    StopDelayingLoadEventsMode(PipelineId),
     /// Sends the final response to script thread for fetching after all redirections
     /// have been resolved
     NavigationResponse(PipelineId, FetchResponseMsg),
@@ -338,6 +342,7 @@ impl fmt::Debug for ConstellationControlMsg {
     fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
         use self::ConstellationControlMsg::*;
         let variant = match *self {
+            StopDelayingLoadEventsMode(..) => "StopDelayingLoadsEventMode",
             NavigationResponse(..) => "NavigationResponse",
             AttachLayout(..) => "AttachLayout",
             Resize(..) => "Resize",
@@ -724,6 +729,8 @@ pub enum ConstellationMsg {
     IsReadyToSaveImage(HashMap<PipelineId, Epoch>),
     /// Inform the constellation of a key event.
     Keyboard(KeyboardEvent),
+    /// Whether to allow script to navigate.
+    AllowNavigationResponse(PipelineId, bool),
     /// Request to load a page.
     LoadUrl(TopLevelBrowsingContextId, ServoUrl),
     /// Request to traverse the joint session history of the provided browsing context.
@@ -768,6 +775,7 @@ impl fmt::Debug for ConstellationMsg {
             GetFocusTopLevelBrowsingContext(..) => "GetFocusTopLevelBrowsingContext",
             IsReadyToSaveImage(..) => "IsReadyToSaveImage",
             Keyboard(..) => "Keyboard",
+            AllowNavigationResponse(..) => "AllowNavigationResponse",
             LoadUrl(..) => "LoadUrl",
             TraverseHistory(..) => "TraverseHistory",
             WindowSize(..) => "WindowSize",