Auto merge of #12426 - asajeffrey:mozbrowser-event-targets, r=SimonSapin

Allow window elements as well as iframes to the the target of mozbrowser events

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Allow mozbrowser events, in particular mozbrowsererror events, to target a window. Needed for https://github.com/browserhtml/browserhtml/issues/1182

---
<!-- 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 #12420
- [X] These changes do not require tests because we're not testing our issue reporting system, which this is intended for.

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components/script/dom/window.rs

@@ -28,7 +28,9 @@ use dom::crypto::Crypto;
 use dom::cssstyledeclaration::{CSSModificationAccess, CSSStyleDeclaration};
 use dom::document::Document;
 use dom::element::Element;
+use dom::event::Event;
 use dom::eventtarget::EventTarget;
+use dom::htmliframeelement::build_mozbrowser_custom_event;
 use dom::location::Location;
 use dom::navigator::Navigator;
 use dom::node::{Node, from_untrusted_node_address, window_from_node};
@@ -63,7 +65,7 @@ use script_runtime::{ScriptChan, ScriptPort, maybe_take_panic_result};
 use script_thread::SendableMainThreadScriptChan;
 use script_thread::{MainThreadScriptChan, MainThreadScriptMsg, RunnableWrapper};
 use script_traits::webdriver_msg::{WebDriverJSError, WebDriverJSResult};
-use script_traits::{ConstellationControlMsg, UntrustedNodeAddress};
+use script_traits::{ConstellationControlMsg, MozBrowserEvent, UntrustedNodeAddress};
 use script_traits::{DocumentState, MsDuration, TimerEvent, TimerEventId};
 use script_traits::{ScriptMsg as ConstellationMsg, TimerEventRequest, TimerSource, WindowSizeData};
 use std::ascii::AsciiExt;
@@ -1588,6 +1590,13 @@ impl Window {
             _ => false,
         }
     }
+
+    #[allow(unsafe_code)]
+    pub fn dispatch_mozbrowser_event(&self, event: MozBrowserEvent) {
+        assert!(PREFS.is_mozbrowser_enabled());
+        let custom_event = build_mozbrowser_custom_event(&self, event);
+        custom_event.upcast::<Event>().fire(self.upcast());
+    }
 }
 
 impl Window {