Use a dictionary-mode code cache on the map rather than a dual system.

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 024e110766f983ac28ec574b435b567331f78ace..33b708dc5bd24a1454498525507c4a741dd1c327 100644
--- a/src/heap/incremental-marking.cc
+++ b/src/heap/incremental-marking.cc
@@ -553,12 +553,6 @@ void IncrementalMarking::StartMarking() {
   heap_->CompletelyClearInstanceofCache();
   heap_->isolate()->compilation_cache()->MarkCompactPrologue();
 
-  if (FLAG_cleanup_code_caches_at_gc) {
-    // We will mark cache black with a separate pass
-    // when we finish marking.
-    MarkObjectGreyDoNotEnqueue(heap_->polymorphic_code_cache());
-  }
-
   // Mark strong roots grey.
   IncrementalMarkingRootMarkingVisitor visitor(this);
   heap_->IterateStrongRoots(&visitor, VISIT_ONLY_STRONG);
@@ -925,13 +919,6 @@ void IncrementalMarking::Hurry() {
     }
   }
 
-  if (FLAG_cleanup_code_caches_at_gc) {
-    PolymorphicCodeCache* poly_cache = heap_->polymorphic_code_cache();
-    Marking::GreyToBlack(Marking::MarkBitFrom(poly_cache));
-    MemoryChunk::IncrementLiveBytesFromGC(poly_cache,
-                                          PolymorphicCodeCache::kSize);
-  }
-
   Object* context = heap_->native_contexts_list();
   while (!context->IsUndefined()) {
     // GC can happen when the context is not fully initialized,