Auto merge of #12416 - canaltinova:referrer, r=jdm

Implement Document.referrer

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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 #12389 (github issue number if applicable).

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components/net/http_loader.rs

@@ -1071,6 +1071,7 @@ pub fn load<A, B>(load_data: &LoadData,
         } else {
             HttpsState::None
         };
+        metadata.referrer = referrer_url;
 
         // Only notify the devtools about the final request that received a response.
         if let Some(msg) = msg {