Auto merge of #17083 - danielj41:javascript-url-global-3, r=jdm

"javascript:" urls: execute in correct global scope

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#### Summary

This pull request makes `javascript:` urls execute in the correct global scope.

#### Example

```html
<script> var x = 4; </script>

<!-- this branch: logs "4" -->
<!-- master: undefined variable error -->
<a href="javascript:console.log(x)">link</a>
```

#### Questions

I'm new to servo and rust, so I'm unsure about these changes. In particular:
  * What's the appropriate place to evaluate the js?
    * I moved it to `handle_navigate`, but I'm not sure if this will catch all occurrences of `javascript:` urls. I also don't know if this will execute in the correct thread and the correct window.
  * What should I do with the result of the js evaluation?
    * I just ignored it. The previous behavior displayed it as the content of a new page load.

---
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #15147, #16718

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- [x] There are tests for these changes

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1 files changed, 2 insertions, 0 deletions

diff --git a/components/script_traits/script_msg.rs b/components/script_traits/script_msg.rs
index 30ae527562e..6ad93d922d4 100644
--- a/components/script_traits/script_msg.rs
+++ b/components/script_traits/script_msg.rs
@@ -99,6 +99,8 @@ pub enum ScriptMsg {
     /// 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),
+    /// Abort loading after sending a LoadUrl message.
+    AbortLoadUrl,
     /// Post a message to the currently active window of a given browsing context.
     PostMessage(BrowsingContextId, Option<ImmutableOrigin>, Vec<u8>),
     /// Dispatch a mozbrowser event to the parent of a mozbrowser iframe.