Bug 1789585 - Add file system as LockedGetUsage client. r=dom-storage-reviewers,janv

Depends on D163699

Differential Revision: https://phabricator.services.mozilla.com/D165322

dom/quota/OriginInfo.cpp

@@ -146,7 +146,8 @@ UsageInfo OriginInfo::LockedGetUsageForClient(Client::Type aClientType) {
   // which only use DatabaseUsage. If this assertion is lifted, the logic below
   // must be adapted.
   MOZ_ASSERT(aClientType == Client::Type::DOMCACHE ||
-             aClientType == Client::Type::LS);
+             aClientType == Client::Type::LS ||
+             aClientType == Client::Type::FILESYSTEM);
 
   return UsageInfo{DatabaseUsageType{mClientUsages[aClientType]}};
 }