Bug 1540401 - Backout Part 1: Convert MOZ_DIAGNOSTIC_ASSERT back to MOZ_ASSERT since bug 1541972 hasn't been fixed yet; r=asuth

dom/localstorage/ActorsParent.cpp

@@ -8632,7 +8632,7 @@ nsresult QuotaClient::InitOrigin(PersistenceType aPersistenceType,
       }
     }
 
-    MOZ_DIAGNOSTIC_ASSERT(usage >= 0);
+    MOZ_ASSERT(usage >= 0);
 
     if (!aForGetUsage) {
       InitUsageForOrigin(aOrigin, usage);