Auto merge of #11468 - rebstar6:refPol4, r=nox

Implement meta referrer policy delivery (3)

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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 #10311 (github issue number if applicable).

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components/script/dom/document.rs

@@ -237,7 +237,7 @@ pub struct Document {
     /// The document's origin.
     origin: Origin,
     ///  https://w3c.github.io/webappsec-referrer-policy/#referrer-policy-states
-    referrer_policy: Option<ReferrerPolicy>,
+    referrer_policy: Cell<Option<ReferrerPolicy>>,
 }
 
 #[derive(JSTraceable, HeapSizeOf)]
@@ -1697,7 +1697,7 @@ impl Document {
             touchpad_pressure_phase: Cell::new(TouchpadPressurePhase::BeforeClick),
             origin: origin,
             //TODO - setting this for now so no Referer header set
-            referrer_policy: Some(ReferrerPolicy::NoReferrer),
+            referrer_policy: Cell::new(Some(ReferrerPolicy::NoReferrer)),
         }
     }
 
@@ -1827,9 +1827,13 @@ impl Document {
         }
     }
 
-    //TODO - for now, returns no-referrer for all until reading in the value
+    pub fn set_referrer_policy(&self, policy: Option<ReferrerPolicy>) {
+        self.referrer_policy.set(policy);
+    }
+
+    //TODO - default still at no-referrer
     pub fn get_referrer_policy(&self) -> Option<ReferrerPolicy> {
-        return self.referrer_policy.clone();
+        return self.referrer_policy.get();
     }
 }
 
@@ -2800,6 +2804,20 @@ fn update_with_current_time_ms(marker: &Cell<u64>) {
     }
 }
 
+/// https://w3c.github.io/webappsec-referrer-policy/#determine-policy-for-token
+pub fn determine_policy_for_token(token: &str) -> Option<ReferrerPolicy> {
+    let lower = token.to_lowercase();
+    return match lower.as_ref() {
+        "never" | "no-referrer" => Some(ReferrerPolicy::NoReferrer),
+        "default" | "no-referrer-when-downgrade" => Some(ReferrerPolicy::NoRefWhenDowngrade),
+        "origin" => Some(ReferrerPolicy::OriginOnly),
+        "origin-when-cross-origin" => Some(ReferrerPolicy::OriginWhenCrossOrigin),
+        "always" | "unsafe-url" => Some(ReferrerPolicy::UnsafeUrl),
+        "" => Some(ReferrerPolicy::NoReferrer),
+        _ => None,
+    }
+}
+
 pub struct DocumentProgressHandler {
     addr: Trusted<Document>
 }