Bug 1845940 - Call RecomputeResistFingerprinting in Document::SetPrincipals. r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D184943

browser/components/resistfingerprinting/test/browser/browser_timezone.js

@@ -152,3 +152,43 @@ add_task(async function test_timezone_exempt_wrong_domain() {
 
   await SpecialPowers.popPrefEnv();
 });
+
+add_task(async function test_timezone_exmpt_browser() {
+  SpecialPowers.Cu.getJSTestingFunctions().setTimeZone("PST8PDT");
+  is(
+    Intl.DateTimeFormat("en-US").resolvedOptions().timeZone,
+    "PST8PDT",
+    "Default time zone should have changed"
+  );
+
+  await SpecialPowers.pushPrefEnv({
+    set: [["privacy.resistFingerprinting", true]],
+  });
+
+  is(
+    Intl.DateTimeFormat("en-US").resolvedOptions().timeZone,
+    "PST8PDT",
+    "Timezone in chrome should be unaffected by resistFingerprinting"
+  );
+
+  let newWindow = Services.ww.openWindow(
+    null,
+    AppConstants.BROWSER_CHROME_URL,
+    "_blank",
+    "chrome,dialog=no,all,alwaysRaised",
+    null
+  );
+
+  is(
+    newWindow.Intl.DateTimeFormat("en-US").resolvedOptions().timeZone,
+    "PST8PDT",
+    "Timezone in new chrome window should be unaffected by resistFingerprinting"
+  );
+
+  newWindow.close();
+
+  await SpecialPowers.popPrefEnv();
+
+  // Reset timezone
+  SpecialPowers.Cu.getJSTestingFunctions().setTimeZone(undefined);
+});

dom/base/Document.cpp

@@ -2787,10 +2787,10 @@ nsresult Document::Init(nsIPrincipal* aPrincipal,
 
   if (aPrincipal) {
     SetPrincipals(aPrincipal, aPartitionedPrincipal);
+  } else {
+    RecomputeResistFingerprinting();
   }
 
-  RecomputeResistFingerprinting();
-
   return NS_OK;
 }
 
@@ -4241,6 +4241,8 @@ void Document::SetPrincipals(nsIPrincipal* aNewPrincipal,
 
   mCSSLoader->RegisterInSheetCache();
 
+  RecomputeResistFingerprinting();
+
 #ifdef DEBUG
   // Validate that the docgroup is set correctly by calling its getter and
   // triggering its sanity check.