Idle sweeping should not schedule a timer callback for more sweeping.

https://bugs.webkit.org/show_bug.cgi?id=259023
rdar://111962239

Reviewed by Wenson Hsieh.

Idle time work should only do work during idle time.  Starting a timer as we come out of
idle will add work that contends with non-idle activity.

* Source/JavaScriptCore/heap/IncrementalSweeper.cpp:
(JSC::IncrementalSweeper::doSweep):

Canonical link: https://commits.webkit.org/265884@main

Source/JavaScriptCore/heap/IncrementalSweeper.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2012-2021 Apple Inc. All rights reserved.
+ * Copyright (C) 2012-2023 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -78,7 +78,8 @@ void IncrementalSweeper::doSweep(VM& vm, MonotonicTime deadline, SweepTrigger tr
         if (MonotonicTime::now() < deadline)
             continue;
 
-        scheduleTimer();
+        if (trigger == SweepTrigger::Timer)
+            scheduleTimer();
         return;
     }