Auto merge of #11542 - asajeffrey:mozbrowser-send-opentab-event, r=paulrouget

Fire a mozbrowseropenwindow event when an html anchor has a non-self target

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When an html anchor has a non-self target, fire a `mozbrowseropenwindow` event.

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<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #11539.
- [X] These changes do not require tests because we don't have the infrastructure for mozbrowser testing yet.

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components/script_traits/lib.rs

@@ -404,8 +404,13 @@ pub enum MozBrowserEvent {
     LoadStart,
     /// Sent when a browser `<iframe>`'s location changes.
     LocationChange(String, bool, bool),
-    /// Sent when window.open() is called within a browser `<iframe>`.
-    OpenWindow,
+    /// Sent when a new tab is opened within a browser `<iframe>` as a result of the user
+    /// issuing a command to open a link target in a new tab (for example ctrl/cmd + click.)
+    /// Includes the URL.
+    OpenTab(String),
+    /// Sent when a new window is opened within a browser `<iframe>`.
+    /// Includes the URL, target browsing context name, and features.
+    OpenWindow(String, Option<String>, Option<String>),
     /// Sent when the SSL state changes within a browser `<iframe>`.
     SecurityChange(HttpsState),
     /// Sent when alert(), confirm(), or prompt() is called within a browser `<iframe>`.
@@ -431,7 +436,8 @@ impl MozBrowserEvent {
             MozBrowserEvent::LoadEnd => "mozbrowserloadend",
             MozBrowserEvent::LoadStart => "mozbrowserloadstart",
             MozBrowserEvent::LocationChange(_, _, _) => "mozbrowserlocationchange",
-            MozBrowserEvent::OpenWindow => "mozbrowseropenwindow",
+            MozBrowserEvent::OpenTab(_) => "mozbrowseropentab",
+            MozBrowserEvent::OpenWindow(_, _, _) => "mozbrowseropenwindow",
             MozBrowserEvent::SecurityChange(_) => "mozbrowsersecuritychange",
             MozBrowserEvent::ShowModalPrompt(_, _, _, _) => "mozbrowsershowmodalprompt",
             MozBrowserEvent::TitleChange(_) => "mozbrowsertitlechange",