[heap] Enable compaction for concurrent marking.

Bug: chromium:694255
Change-Id: Id1ae4eb069a4ba79a35f1bb6b2bc2b1c445edb96
Reviewed-on: https://chromium-review.googlesource.com/600969Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47155}

src/flag-definitions.h

@@ -672,9 +672,6 @@ DEFINE_INT(v8_os_page_size, 0, "override OS page size (in KBytes)")
 DEFINE_BOOL(always_compact, false, "Perform compaction on every full GC")
 DEFINE_BOOL(never_compact, false,
             "Never perform compaction on full GC - testing only")
-// TODO(ulan): enable compaction for concurrent marking when it correctly
-// records slots to evacuation candidates.
-DEFINE_IMPLICATION(concurrent_marking, never_compact)
 DEFINE_BOOL(compact_code_space, true, "Compact code space on full collections")
 DEFINE_BOOL(cleanup_code_caches_at_gc, true,
             "Flush code caches in maps during mark compact cycle.")

src/heap/heap.cc

@@ -6405,7 +6405,6 @@ void Heap::ClearRecordedSlot(HeapObject* object, Object** slot) {
   if (!page->InNewSpace()) {
     DCHECK_EQ(page->owner()->identity(), OLD_SPACE);
     store_buffer()->DeleteEntry(slot_addr);
-    RememberedSet<OLD_TO_OLD>::Remove(page, slot_addr);
   }
 }
 
@@ -6426,8 +6425,6 @@ void Heap::ClearRecordedSlotRange(Address start, Address end) {
   if (!page->InNewSpace()) {
     DCHECK_EQ(page->owner()->identity(), OLD_SPACE);
     store_buffer()->DeleteEntry(start, end);
-    RememberedSet<OLD_TO_OLD>::RemoveRange(page, start, end,
-                                           SlotSet::FREE_EMPTY_BUCKETS);
   }
 }