Reland "Only use FreeSpace objects in the free list"

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index bc55f9e1c5f8fb88a9a3db623d2dba0efd3bc2d9..147d5ddff02578e3fa82428f3672fac83a900712 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -495,11 +495,11 @@ void Heap::ClearAllICsByKind(Code::Kind kind) {
 }
 
 
-void Heap::RepairFreeListsAfterBoot() {
+void Heap::RepairFreeListsAfterDeserialization() {
   PagedSpaces spaces(this);
   for (PagedSpace* space = spaces.next(); space != NULL;
        space = spaces.next()) {
-    space->RepairFreeListsAfterBoot();
+    space->RepairFreeListsAfterDeserialization();
   }
 }
 
@@ -952,14 +952,15 @@ bool Heap::ReserveSpace(Reservation* reservations) {
           } else {
             allocation = paged_space(space)->AllocateRaw(size);
           }
-          FreeListNode* node;
-          if (allocation.To(&node)) {
+          HeapObject* free_space;
+          if (allocation.To(&free_space)) {
             // Mark with a free list node, in case we have a GC before
             // deserializing.
-            node->set_size(this, size);
+            Address free_space_address = free_space->address();
+            CreateFillerObjectAt(free_space_address, size);
             DCHECK(space < Serializer::kNumberOfPreallocatedSpaces);
-            chunk.start = node->address();
-            chunk.end = node->address() + size;
+            chunk.start = free_space_address;
+            chunk.end = free_space_address + size;
           } else {
             perform_gc = true;
             break;
@@ -3392,13 +3393,18 @@ AllocationResult Heap::AllocateByteArray(int length, PretenureFlag pretenure) {
 void Heap::CreateFillerObjectAt(Address addr, int size) {
   if (size == 0) return;
   HeapObject* filler = HeapObject::FromAddress(addr);
+  // At this point, we may be deserializing the heap from a snapshot, and
+  // none of the maps have been created yet and are NULL.
   if (size == kPointerSize) {
-    filler->set_map_no_write_barrier(one_pointer_filler_map());
+    filler->set_map_no_write_barrier(raw_unchecked_one_pointer_filler_map());
+    DCHECK(filler->map() == NULL || filler->map() == one_pointer_filler_map());
   } else if (size == 2 * kPointerSize) {
-    filler->set_map_no_write_barrier(two_pointer_filler_map());
+    filler->set_map_no_write_barrier(raw_unchecked_two_pointer_filler_map());
+    DCHECK(filler->map() == NULL || filler->map() == two_pointer_filler_map());
   } else {
-    filler->set_map_no_write_barrier(free_space_map());
-    FreeSpace::cast(filler)->set_size(size);
+    filler->set_map_no_write_barrier(raw_unchecked_free_space_map());
+    DCHECK(filler->map() == NULL || filler->map() == free_space_map());
+    FreeSpace::cast(filler)->nobarrier_set_size(size);
   }
 }