Bug 1910848 - Add support for pausing QM IO thread after finishing directory work; r=dom-storage-reviewers,hsingh,asuth

Differential Revision: https://phabricator.services.mozilla.com/D194176

dom/quota/OriginOperationBase.cpp

@@ -8,6 +8,7 @@
 
 #include "mozilla/Assertions.h"
 #include "mozilla/MozPromise.h"
+#include "mozilla/StaticPrefs_dom.h"
 #include "mozilla/dom/fs/TargetPtrHolder.h"
 #include "mozilla/dom/quota/OriginOperationCallbacks.h"
 #include "mozilla/dom/quota/QuotaManager.h"
@@ -98,6 +99,12 @@ void OriginOperationBase::RunImmediately() {
                           *selfHolder->mQuotaManager)),
                       CreateAndRejectBoolPromise);
 
+               uint32_t pauseOnIOThreadMs = StaticPrefs::
+                   dom_quotaManager_originOperations_pauseOnIOThreadMs();
+               if (pauseOnIOThreadMs > 0) {
+                 PR_Sleep(PR_MillisecondsToInterval(pauseOnIOThreadMs));
+               }
+
                return BoolPromise::CreateAndResolve(true, __func__);
              })
       ->Then(

modules/libpref/init/StaticPrefList.yaml

@@ -3473,6 +3473,12 @@
   value: -1
   mirror: always
 
+# A pref that is used to slow down origin operations for testing purposes.
+- name: dom.quotaManager.originOperations.pauseOnIOThreadMs
+  type: RelaxedAtomicUint32
+  value: 0
+  mirror: always
+
 # A pref that is used to enable testing features.
 - name: dom.quotaManager.testing
   type: SequentiallyConsistentAtomicBool