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/blob_loader.rs

@@ -46,6 +46,7 @@ pub fn load_blob(load_data: LoadData, start_chan: LoadConsumer,
         // https://w3c.github.io/FileAPI/#TwoHundredOK
         status: Some(RawStatus(200, "OK".into())),
         https_state: HttpsState::None,
+        referrer: None
     };
 
     if let Ok(chan) =