Auto merge of #18181 - paulrouget:close_browser, r=cbrewster

Make it possible to close a browsing context from the embedder

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- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #18006 (github issue number if applicable).

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components/compositing/compositor.rs

@@ -828,6 +828,13 @@ impl<Window: WindowMethods> IOCompositor<Window> {
                 }
             }
 
+            WindowEvent::CloseBrowser(ctx) => {
+                let msg = ConstellationMsg::CloseBrowser(ctx);
+                if let Err(e) = self.constellation_chan.send(msg) {
+                    warn!("Sending CloseBrowser message to constellation failed ({}).", e);
+                }
+            }
+
             WindowEvent::SelectBrowser(ctx) => {
                 let msg = ConstellationMsg::SelectBrowser(ctx);
                 if let Err(e) = self.constellation_chan.send(msg) {