Bring heap snapshot Map iterator up to date.

1. Do not mark code_cache as a weak container.
2. Support layout_descriptor field.

Review-Url: https://codereview.chromium.org/2204133002
Cr-Commit-Position: refs/heads/master@{#38285}

src/objects-inl.h

@@ -5424,13 +5424,13 @@ void Map::set_prototype(Object* value, WriteBarrierMode mode) {
 
 
 LayoutDescriptor* Map::layout_descriptor_gc_safe() {
-  Object* layout_desc = READ_FIELD(this, kLayoutDecriptorOffset);
+  Object* layout_desc = READ_FIELD(this, kLayoutDescriptorOffset);
   return LayoutDescriptor::cast_gc_safe(layout_desc);
 }
 
 
 bool Map::HasFastPointerLayout() const {
-  Object* layout_desc = READ_FIELD(this, kLayoutDecriptorOffset);
+  Object* layout_desc = READ_FIELD(this, kLayoutDescriptorOffset);
   return LayoutDescriptor::IsFastPointerLayout(layout_desc);
 }
 
@@ -5478,8 +5478,7 @@ void Map::InitializeDescriptors(DescriptorArray* descriptors,
 
 
 ACCESSORS(Map, instance_descriptors, DescriptorArray, kDescriptorsOffset)
-ACCESSORS(Map, layout_descriptor, LayoutDescriptor, kLayoutDecriptorOffset)
-
+ACCESSORS(Map, layout_descriptor, LayoutDescriptor, kLayoutDescriptorOffset)
 
 void Map::set_bit_field3(uint32_t bits) {
   if (kInt32Size != kPointerSize) {

src/objects.h

@@ -6260,10 +6260,10 @@ class Map: public HeapObject {
   static const int kDescriptorsOffset =
       kTransitionsOrPrototypeInfoOffset + kPointerSize;
 #if V8_DOUBLE_FIELDS_UNBOXING
-  static const int kLayoutDecriptorOffset = kDescriptorsOffset + kPointerSize;
-  static const int kCodeCacheOffset = kLayoutDecriptorOffset + kPointerSize;
+  static const int kLayoutDescriptorOffset = kDescriptorsOffset + kPointerSize;
+  static const int kCodeCacheOffset = kLayoutDescriptorOffset + kPointerSize;
 #else
-  static const int kLayoutDecriptorOffset = 1;  // Must not be ever accessed.
+  static const int kLayoutDescriptorOffset = 1;  // Must not be ever accessed.
   static const int kCodeCacheOffset = kDescriptorsOffset + kPointerSize;
 #endif
   static const int kDependentCodeOffset = kCodeCacheOffset + kPointerSize;

src/profiler/heap-snapshot-generator.cc

@@ -1289,16 +1289,19 @@ void V8HeapExplorer::ExtractMapReferences(int entry, Map* map) {
   }
   DescriptorArray* descriptors = map->instance_descriptors();
   TagObject(descriptors, "(map descriptors)");
-  SetInternalReference(map, entry,
-                       "descriptors", descriptors,
+  SetInternalReference(map, entry, "descriptors", descriptors,
                        Map::kDescriptorsOffset);
-
-  MarkAsWeakContainer(map->code_cache());
-  SetInternalReference(map, entry,
-                       "code_cache", map->code_cache(),
+  SetInternalReference(map, entry, "code_cache", map->code_cache(),
                        Map::kCodeCacheOffset);
-  SetInternalReference(map, entry,
-                       "prototype", map->prototype(), Map::kPrototypeOffset);
+  SetInternalReference(map, entry, "prototype", map->prototype(),
+                       Map::kPrototypeOffset);
+#if V8_DOUBLE_FIELDS_UNBOXING
+  if (FLAG_unbox_double_fields) {
+    SetInternalReference(map, entry, "layout_descriptor",
+                         map->layout_descriptor(),
+                         Map::kLayoutDescriptorOffset);
+  }
+#endif
   Object* constructor_or_backpointer = map->constructor_or_backpointer();
   if (constructor_or_backpointer->IsMap()) {
     TagObject(constructor_or_backpointer, "(back pointer)");