Auto merge of #23368 - gterzian:clean_up_navigation, r=asajeffrey

Clean-up navigation

<!-- Please describe your changes on the following line: -->

1. Navigation as a result of following a hyperlink should be done in a task: https://html.spec.whatwg.org/multipage/links.html#following-hyperlinks:dom-manipulation-task-source
2. The javascript url navigation should also be done in a task: https://html.spec.whatwg.org/multipage/browsing-the-web.html#navigating-across-documents:dom-manipulation-task-source
3. In `window.load_url`, it seems there is no need to send a message to the script-thread(the entirety of `load_url` should instead be done in a task when appropriate), so we can just do that last part "sync" by calling a method on the script, which will send a message to the constellation(for the parallel navigation steps), or queue task(for the JS navigation), as appropriate.
4. Separate the "normal" navigation flow from the handling of "navigate an iframe" message from constellation, since doing everything in one method as was previously done with `handle_navigate`, is confusing.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `___` with appropriate data: -->
- [ ] `./mach build -d` does not report any errors
- [ ] `./mach test-tidy` does not report any errors
- [ ] These changes fix #___ (GitHub issue number if applicable)

<!-- Either: -->
- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because ___

<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/23368)
<!-- Reviewable:end -->

components/script_traits/script_msg.rs

@@ -5,7 +5,6 @@
 use crate::AnimationState;
 use crate::AuxiliaryBrowsingContextLoadInfo;
 use crate::DocumentState;
-use crate::IFrameLoadInfo;
 use crate::IFrameLoadInfoWithData;
 use crate::LayoutControlMsg;
 use crate::LoadData;
@@ -97,6 +96,15 @@ pub enum LogEntry {
     Warn(String),
 }
 
+/// https://html.spec.whatwg.org/multipage/#replacement-enabled
+#[derive(Debug, Deserialize, Serialize)]
+pub enum HistoryEntryReplacement {
+    /// Traverse the history with replacement enabled.
+    Enabled,
+    /// Traverse the history with replacement disabled.
+    Disabled,
+}
+
 /// Messages from the script to the constellation.
 #[derive(Deserialize, Serialize)]
 pub enum ScriptMsg {
@@ -143,7 +151,7 @@ pub enum ScriptMsg {
     LoadComplete,
     /// A new load has been requested, with an option to replace the current entry once loaded
     /// instead of adding a new entry.
-    LoadUrl(LoadData, bool),
+    LoadUrl(LoadData, HistoryEntryReplacement),
     /// Abort loading after sending a LoadUrl message.
     AbortLoadUrl,
     /// Post a message to the currently active window of a given browsing context.
@@ -158,7 +166,7 @@ pub enum ScriptMsg {
         data: Vec<u8>,
     },
     /// Inform the constellation that a fragment was navigated to and whether or not it was a replacement navigation.
-    NavigatedToFragment(ServoUrl, bool),
+    NavigatedToFragment(ServoUrl, HistoryEntryReplacement),
     /// HTMLIFrameElement Forward or Back traversal.
     TraverseHistory(TraversalDirection),
     /// Inform the constellation of a pushed history state.
@@ -175,7 +183,7 @@ pub enum ScriptMsg {
     /// A load has been requested in an IFrame.
     ScriptLoadedURLInIFrame(IFrameLoadInfoWithData),
     /// A load of the initial `about:blank` has been completed in an IFrame.
-    ScriptNewIFrame(IFrameLoadInfo, IpcSender<LayoutControlMsg>),
+    ScriptNewIFrame(IFrameLoadInfoWithData, IpcSender<LayoutControlMsg>),
     /// Script has opened a new auxiliary browsing context.
     ScriptNewAuxiliary(
         AuxiliaryBrowsingContextLoadInfo,