[heap] Remove unecessary marking bit check in RecordWriteSlow.

src/heap/incremental-marking.cc

Index: src/heap/incremental-marking.cc
diff --git a/src/heap/incremental-marking.cc b/src/heap/incremental-marking.cc
index 6d759253dff79dfa6362d97af8547ce733de1b5b..c72effc08fb36ed83e1f16f24695f0175a0895b4 100644
--- a/src/heap/incremental-marking.cc
+++ b/src/heap/incremental-marking.cc
@@ -80,11 +80,8 @@ bool IncrementalMarking::BaseRecordWrite(HeapObject* obj, Object** slot,
 void IncrementalMarking::RecordWriteSlow(HeapObject* obj, Object** slot,
                                          Object* value) {
   if (BaseRecordWrite(obj, slot, value) && slot != NULL) {

[Hannes Payer (out of office), 2015/11/03 22:51:14]

BaseRecordWrite already tells us if we have to record the slot, i.e. checks the
color of obj. No need to do it again.

[Michael Lippautz, 2015/11/03 22:54:25]

Acknowledged.

-    MarkBit obj_bit = Marking::MarkBitFrom(obj);
-    if (Marking::IsBlack(obj_bit)) {
-      // Object is not going to be rescanned we need to record the slot.
-      heap_->mark_compact_collector()->RecordSlot(obj, slot, value);
-    }
+    // Object is not going to be rescanned we need to record the slot.
+    heap_->mark_compact_collector()->RecordSlot(obj, slot, value);
   }
 }