Support slots recording for compaction during incremental marking.

src/incremental-marking-inl.h

Index: src/incremental-marking-inl.h
diff --git a/src/incremental-marking-inl.h b/src/incremental-marking-inl.h
index c82d67845622451f958950b75a3445429d4cf8aa..94f52eefaa546075a15f6a02d5332e57100cc3c8 100644
--- a/src/incremental-marking-inl.h
+++ b/src/incremental-marking-inl.h
@@ -34,7 +34,9 @@ namespace v8 {
 namespace internal {
 
 
-void IncrementalMarking::RecordWrite(HeapObject* obj, Object* value) {
+void IncrementalMarking::RecordWrite(HeapObject* obj,
+                                     Object** slot,
+                                     Object* value) {
   if (IsMarking() && value->IsHeapObject()) {
     MarkBit value_bit = Marking::MarkBitFrom(HeapObject::cast(value));
     if (Marking::IsWhite(value_bit)) {
@@ -43,6 +45,18 @@ void IncrementalMarking::RecordWrite(HeapObject* obj, Object* value) {
         BlackToGreyAndUnshift(obj, obj_bit);
         RestartIfNotMarking();
       }
+
+      // Object is either grey or white it will be scanned if survives.
+      return;
+    }
+
+    if (is_compacting_ && slot != NULL) {
+      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(
+            HeapObject::RawField(obj, 0), slot, value);
+      }
     }
   }
 }
@@ -50,6 +64,8 @@ void IncrementalMarking::RecordWrite(HeapObject* obj, Object* value) {
 
 void IncrementalMarking::RecordWriteOf(HeapObject* value) {
   if (IsMarking()) {
+    ASSERT(!MarkCompactCollector::IsOnEvacuationCandidate(value));
+
     MarkBit value_bit = Marking::MarkBitFrom(value);
     if (Marking::IsWhite(value_bit)) {
       WhiteToGreyAndPush(value, value_bit);