[heap] Remove unused flag prohibiting local slot buffer entries

src/heap/mark-compact.h

Index: src/heap/mark-compact.h
diff --git a/src/heap/mark-compact.h b/src/heap/mark-compact.h
index 527916e135017c2292c1c7030ab8a5c48c249392..22bb8f1f597718f2eb78a93bf28ff2d20f5dfddf 100644
--- a/src/heap/mark-compact.h
+++ b/src/heap/mark-compact.h
@@ -767,9 +767,6 @@ class MarkCompactCollector {
   // True if concurrent or parallel sweeping is currently in progress.
   bool sweeping_in_progress_;
 
-  // True if parallel compaction is currently in progress.
-  bool compaction_in_progress_;
-
   // Semaphore used to synchronize sweeper tasks.
   base::Semaphore pending_sweeper_tasks_semaphore_;