Bug 1786256 - Let network.cache.shutdown_purge_in_background_task=true ride the trains r=necko-reviewers,kershaw

Differential Revision: https://phabricator.services.mozilla.com/D162190

modules/libpref/init/StaticPrefList.yaml

@@ -11886,7 +11886,7 @@
 # delete the cache folder at shutdown in order to avoid shutdown hangs.
 - name: network.cache.shutdown_purge_in_background_task
   type: RelaxedAtomicBool
-#if defined(NIGHTLY_BUILD) && defined(XP_WIN)
+#if defined(XP_WIN)
   value: true
 #else
   value: false

netwerk/cache2/CacheFileIOManager.cpp

@@ -1382,10 +1382,8 @@ nsresult CacheFileIOManager::OnDelayedStartupFinished() {
 
   return target->Dispatch(
       NS_NewRunnableFunction("CacheFileIOManager::OnDelayedStartupFinished",
-                             [ioMan = RefPtr{ioMan}] {
-                               // TODO: Check if there are any old cache dirs.
-                               // Report telemetry.
-                               gInstance->DispatchPurgeTask(""_ns, "0"_ns,
+                             [ioMan = std::move(ioMan)] {
+                               ioMan->DispatchPurgeTask(""_ns, "0"_ns,
                                                         kPurgeExtension);
                              }),
       nsIEventTarget::DISPATCH_NORMAL);