Allow compaction when incremental marking is on.

src/heap/incremental-marking.h

Index: src/heap/incremental-marking.h
diff --git a/src/heap/incremental-marking.h b/src/heap/incremental-marking.h
index 8ad12bc79f95065c3c30efbc1f0389e35135ce22..4bcb1b433e65e01ad4372b2216cf57950e738f17 100644
--- a/src/heap/incremental-marking.h
+++ b/src/heap/incremental-marking.h
@@ -62,9 +62,7 @@ class IncrementalMarking {
 
   bool WasActivated();
 
-  enum CompactionFlag { ALLOW_COMPACTION, PREVENT_COMPACTION };
-
-  void Start(CompactionFlag flag = ALLOW_COMPACTION);
+  void Start();
 
   void Stop();
 
@@ -203,7 +201,7 @@ class IncrementalMarking {
 
   void ResetStepCounters();
 
-  void StartMarking(CompactionFlag flag);
+  void StartMarking();
 
   void ActivateIncrementalWriteBarrier(PagedSpace* space);
   static void ActivateIncrementalWriteBarrier(NewSpace* space);