Bug 1465294 Part 14 - Use a single thread in stylo when recording/replaying, r=xidorn.

--HG--
extra : rebase_source : b15f4a8889bb2e379a75fabf331a79502a84dc7e

toolkit/recordreplay/ProcessRecordReplay.cpp

@@ -152,6 +152,9 @@ RecordReplayInterface_Initialize(int aArgc, char* aArgv[])
   InitializeCountdownThread();
   SetupDirtyMemoryHandler();
 
+  // Don't create a stylo thread pool when recording or replaying.
+  putenv((char*) "STYLO_THREADS=1");
+
   thread->SetPassThrough(false);
 
   Lock::InitializeLocks();