Backed out 5 changesets (bug 1765313, bug 1770403) for causing bc failures on browser_storageAccessPrivilegeAPI.js. CLOSED TREE

Backed out changeset 22153c8641e1 (bug 1765313)
Backed out changeset 588d54f796a0 (bug 1765313)
Backed out changeset 2376ca53eb9c (bug 1765313)
Backed out changeset 9cf02ec5657a (bug 1770403)
Backed out changeset 7d8147ba25e8 (bug 1770403)

docshell/base/nsDocShell.cpp

@@ -2743,9 +2743,29 @@ nsresult nsDocShell::SetDocLoaderParent(nsDocLoader* aParent) {
     mContentListener->SetParentContentListener(parentURIListener);
   }
 
+  // Inform windows when they're being removed from their parent.
+  if (!aParent) {
+    MaybeClearStorageAccessFlag();
+  }
+
   return NS_OK;
 }
 
+void nsDocShell::MaybeClearStorageAccessFlag() {
+  if (mScriptGlobal) {
+    // Tell our window that the parent has now changed.
+    mScriptGlobal->ParentWindowChanged();
+
+    // Tell all of our children about the change recursively as well.
+    for (auto* childDocLoader : mChildList.ForwardRange()) {
+      nsCOMPtr<nsIDocShell> child = do_QueryObject(childDocLoader);
+      if (child) {
+        static_cast<nsDocShell*>(child.get())->MaybeClearStorageAccessFlag();
+      }
+    }
+  }
+}
+
 void nsDocShell::MaybeRestoreWindowName() {
   if (!StaticPrefs::privacy_window_name_update_enabled()) {
     return;